Your FREE EPA Section 608 Certification Practice Test 2026 – 260+ Q&A

Correct answer: Stratosphere

The protective ozone layer sits in the "stratosphere", roughly 6 to 30 miles up and above the weather, and chlorine carried there by CFCs and HCFCs is what thins it. The "troposphere" is the layer nearest the ground, where weather forms and where ozone is a pollutant rather than a shield. The "mesosphere" and the "thermosphere" are higher layers that hold very little ozone.

Correct answer: Stratospheric ultraviolet light releasing chlorine from stable molecules

A CFC or HCFC molecule is so stable that it stays intact until it reaches the stratosphere, so the cause is "stratospheric ultraviolet light releasing chlorine from stable molecules", and that chlorine goes on destroying ozone for years. "Stratospheric ultraviolet light releasing fluorine from stable molecules" names the wrong atom, because fluorine ends up in stable compounds that do not attack ozone. "Warm surface air releasing chlorine from unstable molecules" has the stability backward, since chlorine freed in the lower air is washed out by rain, and "warm surface air releasing fluorine from unstable molecules" makes both mistakes.

Correct answer: Chlorine carried up to deplete the ozone layer

Because the molecule does not break down near the ground, the result is "chlorine carried up to deplete the ozone layer". "Chlorine locked away inside the ozone layer" is wrong because ultraviolet light in the stratosphere finally splits the molecule and frees the chlorine. "Chlorine rained out beneath the ozone layer" describes soluble chlorine compounds, not a stable refrigerant that does not dissolve in rain. "Chlorine swept to space beyond the ozone layer" is wrong because the molecule is broken apart in the stratosphere and does not escape the atmosphere.

Correct answer: Skin cancers and cataracts

A thinner ozone layer lets more ultraviolet radiation reach the surface, which brings higher rates of "skin cancers and cataracts". "Asthma and bronchitis" belong to ground-level smog, a separate air-quality problem. "Heat stroke and exhaustion" are tied to heat and a warming climate, not to ultraviolet exposure. "Frostbite and asphyxiation" are the direct hazards of handling refrigerant, not effects of ozone loss.

Correct answer: The one rated 4 traps far less heat per pound

Global warming potential compares the heat a gas traps with the heat trapped by the same mass of carbon dioxide, so "the one rated 4 traps far less heat per pound". "The one rated 1,400 traps far less heat per pound" reads the scale backward: the higher number means more warming. "The one rated 4 depletes far less ozone per pound" and "the one rated 1,400 depletes far less ozone per pound" both mistake the rating for ozone depletion potential, which is a separate number that global warming potential says nothing about.

Correct answer: Carbon dioxide

Global warming potential is measured against "carbon dioxide", which is assigned a value of 1. "Refrigerant R-11" is the reference for the other scale, ozone depletion potential, where it is given a value of 1. "Methane" and "nitrous oxide" are greenhouse gases that are themselves rated against carbon dioxide rather than used as the reference.

Correct answer: Zero ozone depletion, strong climate warming

A zero ozone depletion potential with a high global warming potential, as with many HFCs, means "zero ozone depletion, strong climate warming", which is why such refrigerants are still regulated. "Heavy ozone depletion, slight climate warming" reverses the two ratings. "Zero ozone depletion, slight climate warming" treats a zero ozone rating as if it also meant a low warming rating. "Heavy ozone depletion, strong climate warming" describes a CFC, whose ozone depletion potential is high rather than zero.

Correct answer: ODP and GWP

The pair is "ODP and GWP": ozone depletion potential rates the effect on the ozone layer and global warming potential rates the heat-trapping effect on climate. "PEL and TLV" are workplace exposure limits (permissible exposure limit and threshold limit value). "LFL and UFL" are the lower and upper flammability limits. "COP and EER" are efficiency measures (coefficient of performance and energy efficiency ratio).

Correct answer: 1987

The Montreal Protocol, the treaty that set the phase-out schedule for ozone-depleting substances, was signed in 1987. The year 1992 is the Copenhagen Amendment, which tightened the schedule the treaty had already set. The year 1990 is when the U.S. Clean Air Act Amendments created Section 608 and when the treaty was strengthened in London. The year 2016 is the Kigali Amendment, which added the phasedown of HFCs.

Correct answer: Temporary substitutes with reduced ozone depletion potential

HCFCs still contain chlorine, but far less of it reaches the stratosphere, so they served as "temporary substitutes with reduced ozone depletion potential" while chlorine-free refrigerants were developed. "Permanent substitutes with reduced ozone depletion potential" is wrong because HCFCs were always scheduled for their own phase-out. "Temporary substitutes with zero ozone depletion potential" is wrong because an HCFC such as R-22 still depletes some ozone; a rating of zero belongs to HFCs and HFOs. "Permanent substitutes with zero ozone depletion potential" makes both mistakes.

Correct answer: Recycled or reclaimed R-22 recovered from existing systems

With production and import ended on January 1, 2020, service depends on R-22 that already exists, so the legal route is "recycled or reclaimed R-22 recovered from existing systems"; R-22 made before 2020 and still in stock may also be used. "Newly produced or imported R-22 allocated to existing systems" is not possible, because the servicing allowances that permitted limited production and import ended in 2020. "Newly produced or imported R-22 labeled as service stock" is barred because the ban covers newly made R-22 whatever its intended use. "Recycled or reclaimed R-22 mixed with a substitute refrigerant" creates a contaminated mixture that cannot be used or easily reclaimed.

Correct answer: Stronger ozone depletion from CFCs

CFCs have the highest ozone depletion potentials, which is the reason for the order: "stronger ozone depletion from CFCs" meant that ending them first gave the largest benefit, while lower-rated HCFCs bridged the gap. "Easier system conversion from CFCs" is false, because replacing R-11 and R-12 meant new refrigerants, oils and equipment across the industry. "Elevated toxicity risk from CFCs" and "elevated fire hazard from CFCs" are both wrong, since the common CFCs are low in toxicity and nonflammable.

Correct answer: The Clean Air Act

Section 608 is part of "the Clean Air Act", added by the 1990 amendments, and directs EPA to regulate refrigerant handling in stationary equipment. "The Clean Water Act" governs discharges to water. "The Energy Policy Act" and "the Energy Security Act" deal with energy supply and energy use, not refrigerant emissions.

Correct answer: Federal prohibition of knowing releases

The heart of Section 608 is the venting prohibition, the "federal prohibition of knowing releases", which covers service, maintenance, repair and disposal. "Mandatory reclaiming of recovered refrigerant" is false, because recovered refrigerant may go back into the same owner's equipment without reclaiming. "Mandatory Universal certification of technicians" overstates the rule, since the certification type only has to match the equipment. "Deep evacuation of appliances awaiting service" is also false, because required evacuation levels depend on the equipment and many repairs do not open the refrigerant circuit.

Correct answer: As a de minimis release, which the venting ban allows

A tiny, unavoidable loss while hoses are connected or disconnected in good faith is treated "as a de minimis release, which the venting ban allows"; it is not a violation. "As a knowing release, which the venting ban forbids" describes deliberately letting refrigerant escape, which is not what happened here. "As a de minimis release, which needs reporting to EPA" adds a reporting duty that does not exist for these small losses, and "as a knowing release, which needs reporting to EPA" gets both the category and the duty wrong.

Correct answer: The venting prohibition covers disposal work

The prohibition on knowingly releasing refrigerant applies at disposal just as it does during service, so "the venting prohibition covers disposal work": the charge is recovered before the unit is dismantled. "Recovery at disposal belongs to certified reclaimers" is wrong, because a properly certified technician recovers the charge; a reclaimer only reprocesses it afterward. "The EPA notification rule covers disposal work" invents a notice that the rule does not require. "Recovery at disposal belongs to scrap yards" does not fit a chiller, which has to be evacuated before it is taken apart for disposal.

Correct answer: Reclaimed refrigerant of verified new-product purity

AHRI Standard 700 is the purity specification for reclaimed refrigerant, so the label means "reclaimed refrigerant of verified new-product purity", confirmed by chemical analysis. "Recycled refrigerant of verified new-product purity" names the wrong process, because recycling is field cleaning with no laboratory verification. "Reclaimed refrigerant of untested purity from field filtering" understates reclaiming, which must meet every limit in the standard and be tested. "Recycled refrigerant of untested purity from field filtering" describes ordinary recycling, which earns no such label.

Correct answer: Recycling refrigerant for same-owner reuse

A recovery and recycling machine cleans refrigerant by separating oil and passing it through filter-driers, which is enough for "recycling refrigerant for same-owner reuse". "Recycling refrigerant for commercial resale" is not allowed, because used refrigerant that changes ownership must first be reclaimed. "Reclaiming refrigerant for same-owner reuse" and "reclaiming refrigerant for commercial resale" both fail because reclaiming means reprocessing and testing to AHRI 700 purity, which a field machine cannot do; that work belongs to a certified reclaimer.

Correct answer: Recovery

Removing refrigerant from a system and storing it in an external container, in whatever condition it is in, is "recovery". "Recycling" adds cleaning by oil separation and filter-driers. "Reclamation" adds reprocessing and testing to new-product purity. "Destruction" is the permanent breakdown of unwanted refrigerant at an approved facility, not storage.

Correct answer: Reprocessing to verified new-product purity

The basic difference is the standard reached: reclamation means "reprocessing to verified new-product purity", while recycling cleans refrigerant in the field without meeting or verifying that standard. Reclaimed refrigerant is reprocessed to AHRI 700 and confirmed by chemical analysis; recycled refrigerant has only had oil, moisture and particles reduced. "Refrigerant transfer into storage cylinders" confuses reclaiming with recovery. "On-site filtering by the service technician" has the locations reversed, since reclaiming is done at a reclaimer's plant. "Mandatory return to the original owner" is also reversed, since only reclaimed refrigerant may be sold to a new owner.

Correct answer: 40 pounds

A recovery cylinder is filled to no more than 80 percent of its capacity, and 80 percent of 50 pounds is 40 pounds, which leaves vapor space for the liquid to expand as it warms. Filling to 50 pounds uses the full rated capacity and leaves no room for expansion. Stopping at 10 pounds takes the 20 percent headspace for the fill. Filling to 45 pounds applies 90 percent, a figure from small-appliance recovery rather than the cylinder fill rule.

Correct answer: Department of Transportation

Cylinders that store and ship recovered refrigerant must meet the specifications of the "Department of Transportation", which regulates containers for hazardous materials in transport. The "Environmental Protection Agency" writes the recovery and venting rules but does not approve cylinders. The "Department of Labor" covers workplace safety through OSHA. The "National Fire Protection Association" publishes fire and electrical codes and approves no cylinders.

Correct answer: An overdue five-year retest, requiring recertification

Refillable recovery cylinders must be hydrostatically retested every five years, so a stamp eight years old means "an overdue five-year retest, requiring recertification" before the cylinder is used again. "An overdue five-year retest, requiring disposal" goes too far, because a cylinder that passes the retest goes back into service. "A ten-year retest interval, leaving the cylinder usable" and "a twelve-year retest interval, leaving the cylinder usable" borrow longer intervals that apply to other kinds of cylinders, not to refrigerant recovery cylinders.

Correct answer: Hydrostatic rupture of the cylinder as the liquid expands

Liquid refrigerant expands as it warms, and a cylinder with no vapor space has nowhere for that expansion to go, so the danger is "hydrostatic rupture of the cylinder as the liquid expands"; the 80 percent limit keeps a vapor cushion. "Thermal breakdown of the liquid as the cylinder overheats" needs flame or red-hot metal, not a hot day. "Ignition of the cylinder vapor as the liquid boils" does not fit common refrigerants, which are nonflammable or need an ignition source. "Freeze-up of the cylinder valve as the liquid flashes" happens when refrigerant is released quickly and is not the hazard the fill rule addresses.

Correct answer: Gray body and yellow top

A recovery cylinder is marked by a "gray body and yellow top", which sets it apart from cylinders of new refrigerant. A "light blue body and top" was the color long assigned to R-134a, a "light green body and top" to R-22, and a "white body and top" to R-12; each of those marked a cylinder of virgin refrigerant, not a container for recovered refrigerant.

Correct answer: A recovery cylinder for storage

Gray with a yellow top is the code for a refillable recovery container, so it is "a recovery cylinder for storage": it holds recovered refrigerant of unknown condition, not virgin product for charging. "A nitrogen cylinder for leak testing" is wrong because nitrogen comes in tall high-pressure cylinders that carry their own markings. "An oxygen cylinder for brazing" and "an acetylene cylinder for torch work" name torch gases, which are never packaged in gray cylinders with yellow tops.

Correct answer: The Significant New Alternatives Policy program

Substitutes for ozone-depleting substances are reviewed under "the Significant New Alternatives Policy program", known as SNAP, which lists each one as acceptable, acceptable with use conditions, or unacceptable. "The Responsible Appliance Disposal program" is a voluntary partnership for scrapping old appliances. "The GreenChill Advanced Refrigeration Partnership program" is a voluntary partnership with supermarkets to cut refrigerant emissions. "The Toxics Release Inventory program" collects reports of toxic chemical releases from industrial facilities and does not evaluate refrigerant substitutes.

Correct answer: Use restricted to the listed conditions

A substitute listed as acceptable subject to use conditions is acceptable on those terms and no others, so the listing means "use restricted to the listed conditions", whoever installs or services it. "Unrestricted use once the manufacturer complies" is wrong because the conditions bind whoever installs and services the equipment as well. "Wider use with written owner consent" is wrong because an owner cannot waive a federal listing. "Unrestricted use in residential air conditioning" invents an exemption; a listing applies to the end use it names.

Correct answer: A compatible oil specified by the SNAP listing and manufacturer

A substitute refrigerant needs a lubricant it can carry back to the compressor, so the retrofit calls for "a compatible oil specified by the SNAP listing and manufacturer". "A mineral oil miscible with HFCs and HFOs" is false, because mineral oil does not mix with those refrigerants, which is the usual reason for the oil change. "A polyalkylene glycol oil suited to new chillers and heat pumps" is false, because those oils are used mainly in motor vehicle air conditioning, while stationary equipment generally uses polyolester oil. "A doubled oil charge offsetting wear and diminished miscibility" is false, because overcharging oil reduces heat transfer and can damage the compressor; the amount stays at the specified charge.

Correct answer: HFOs

Hydrofluoroolefins are "HFOs": they have zero ozone depletion potential, very low global warming potential, and many are rated A2L. "CFCs" are chlorofluorocarbons and "HCFCs" are hydrochlorofluorocarbons; both contain chlorine and deplete ozone. "HFCs" are hydrofluorocarbons, which are chlorine-free but saturated compounds with much higher global warming potentials.

Correct answer: HCFC

Hydrogen, chlorine, fluorine and carbon together spell out a hydrochlorofluorocarbon, an "HCFC" such as R-22. A "CFC" has chlorine, fluorine and carbon but no hydrogen. An "HFC" has hydrogen, fluorine and carbon but no chlorine. A "halon" contains bromine and is a fire-suppression agent rather than a member of this group.

Correct answer: Chlorine atoms

Chlorine is the atom that destroys ozone: CFCs and HCFCs carry "chlorine atoms" and HFCs and HFOs do not, which gives the second pair an ozone depletion potential of zero. "Fluorine atoms" cannot be the reason because all four families contain fluorine. "Hydrogen atoms" cannot be the reason because CFCs have no hydrogen while HFCs and HFOs do. "Bromine atoms" belong to halons, the bromine compounds used in fire suppression, not to these refrigerants.

Correct answer: HFOs or HFO blends

The lower-GWP A2L refrigerants that replace R-410A are most often "HFOs or HFO blends", such as R-454B, a blend of the HFC R-32 and the hydrofluoroolefin R-1234yf; they have zero ozone depletion potential and are mildly flammable. "CFCs or CFC blends" and "HCFCs or HCFC blends" are ozone-depleting families that have been phased out and none of them is rated A2L. "Hydrocarbons or hydrocarbon blends" such as propane are rated A3, a higher flammability class than A2L.

Correct answer: They are heavier than air and displace the oxygen in low areas

Refrigerant vapor is denser than air, so a leak sinks and collects in a basement or pit: "they are heavier than air and displace the oxygen in low areas", and a person can suffocate without warning. "They are heavier than air and form toxic phosgene in low areas" has the density right but the hazard wrong, because phosgene forms only when certain refrigerants meet an open flame or a very hot surface, not because the vapor settles. "They are lighter than air and displace the oxygen up high" has the density backward, and "they are lighter than air and form toxic phosgene up high" makes both mistakes.

Correct answer: Restoring a safe oxygen level

A large leak pushes breathable air out of the room, and the reason for ventilating first is "restoring a safe oxygen level" before anyone goes in. "Cooling a warm equipment room" is not the purpose; ventilation after a leak is about the air people breathe, not the room temperature. "Keeping moisture out of the system" confuses room ventilation with dehydrating a system. "Removing the refrigerant odor" is wrong because most refrigerants have little or no odor, which is exactly why the oxygen hazard goes unnoticed.

Correct answer: An oxygen deprivation sensor

A device that watches the oxygen percentage and starts alarms and exhaust fans when it falls is "an oxygen deprivation sensor", also called an oxygen depletion sensor. "An oxygen enrichment sensor" works in the other direction: it alarms when oxygen rises above normal, as it can where oxygen is stored. "A refrigerant vapor detector" also protects a machinery room, but it responds to the refrigerant concentration in the room, not to the oxygen level. "A refrigerant leak detector" is the handheld tool used to pinpoint a leak; it does not measure oxygen or control ventilation.

Correct answer: A self-contained breathing apparatus with an air cylinder

When oxygen itself is short, the wearer needs breathing air brought in, which means "a self-contained breathing apparatus with an air cylinder". "A half-mask respirator with an organic vapor cartridge", "a powered air-purifying respirator with a particle filter" and "a full-face gas mask with a chemical canister" all work by cleaning the surrounding air; none of them adds oxygen, so none protects in an oxygen-deficient space.

Correct answer: Parts per million by volume

An exposure limit is an airborne concentration, normally given in "parts per million by volume" of air and averaged over a work shift. "Percent per year of the full charge" is how an appliance leak rate is stated. "Pounds per thousand cubic feet" is how the allowable quantity of refrigerant in an occupied space is stated in building safety standards. "Grains of moisture per pound of dry air" is a measure of humidity.

Correct answer: An unsafe exposure level, requiring protective gear

A reading well over the exposure limit means "an unsafe exposure level, requiring protective gear" for anyone who remains; without proper respiratory protection workers should leave until the space is ventilated. "A short-term excursion, requiring a repeated sample" is wrong, because a concentration well over a limit calls for action, not another measurement. "An ignition hazard, requiring electrical shutdown" confuses the parts-per-million exposure limit with a flammability limit, which is a far higher concentration stated in percent. "A leak rate trigger, requiring prompt repair" confuses an air reading with the annual leak rate of an appliance.

Correct answer: Asphyxiation as the vapor displaces oxygen

Refrigerant vapor is heavier than air, so a large release pushes the breathable air out of a low or enclosed space: 'Asphyxiation as the vapor displaces oxygen' is the main way a low-toxicity refrigerant kills. 'Lung damage as the vapor turns to phosgene' needs an open flame or a very hot surface to decompose the refrigerant, which a high concentration alone does not do; 'Frostbite as the vapor freezes lung tissue' borrows the injury that liquid refrigerant causes on skin and eyes, which is not what kills; 'Chemical burns as the vapor turns to acids' describes what moisture and heat do inside a contaminated system, not what happens in the air a person breathes.

Correct answer: Toxicity at smaller concentrations

In the ASHRAE 34 safety classification the letter gives toxicity and the number gives flammability. Class B is the higher-toxicity group, so the answer is 'Toxicity at smaller concentrations': the exposure limit of a class B refrigerant is lower than that of a class A refrigerant. 'Toxicity at larger concentrations' swaps the meaning of the two letters. 'Flammability at smaller concentrations' and 'Flammability at larger concentrations' both read the letter as a flammability rating, which is carried by the number that follows it (1, 2L, 2 or 3).

Correct answer: Low toxicity, nonflammable

The letter A means lower toxicity and the number 1 means the refrigerant does not propagate a flame, so A1 is 'Low toxicity, nonflammable' (R-134a and R-410A are examples; they still must be recovered). 'Low toxicity, highly flammable' is class A3, such as propane; 'High toxicity, nonflammable' is class B1, such as R-123; 'High toxicity, highly flammable' is class B3.

Correct answer: Recovery needed on disposal and needed on repair

The venting prohibition does not depend on where the refrigerant is going, so the correct comparison is 'Recovery needed on disposal and needed on repair': the charge is recovered and never released, whether the appliance is being disposed of or repaired. 'Recovery needed on disposal and waived on repair' forgets that opening a system for service also requires recovery first; 'Recovery waived on disposal and needed on repair' forgets that refrigerant must be removed before disposal; 'Recovery waived on disposal and waived on repair' treats a leaking unit as exempt, and a leak does not lift the requirement to recover what remains.

Correct answer: Confirming the refrigerant-oil combination against the SNAP listing beforehand

A substitute is acceptable only for the end use and under the use conditions in its SNAP listing, so the prudent answer is 'Confirming the refrigerant-oil combination against the SNAP listing beforehand': the oil stays out of the system until the combination is shown to be consistent with that listing. 'Unrestricted use of the lubricant alongside whichever refrigerant holds a SNAP listing' is wrong because a listing says nothing of the kind and many substitutes need a specific oil; 'Trusting the supplier compatibility claim in place of the SNAP listing' is wrong because marketing does not replace an EPA decision; 'Switching to mineral oil, the single lubricant accepted in a SNAP listing' is wrong because mineral oil does not mix properly with most HFC substitutes, which use polyolester oil.

Correct answer: Severe ozone and severe climate harm from the CFC, minimal harm from the HFO

An ODP of 1.0 and a GWP of 10,900 put the CFC at the damaging end of both scales, and an ODP of 0 with a GWP of 4 puts the HFO near the bottom of both, so 'Severe ozone and severe climate harm from the CFC, minimal harm from the HFO' is the fair summary. 'Severe ozone and slight climate harm from the CFC, minimal harm from the HFO' ignores the CFC's GWP of 10,900; 'Severe ozone and severe climate harm from the CFC, serious harm from the HFO' treats the HFO as if it had the high GWP of an HFC, when its ODP is 0 and its GWP is only 4; 'Severe ozone and slight climate harm from the CFC, serious harm from the HFO' makes both mistakes.

Correct answer: Mild flammability versus no flame propagation

Each option gives the A2L property first and the A1 property second. Class 1 means no flame propagation and class 2L means lower flammability with a slow burning velocity, so 'Mild flammability versus no flame propagation' is why ignition sources matter only for the A2L charge. 'Very high flammability versus mild flammability' overstates both classes: the highest flammability describes class 3, such as propane, and mild flammability describes class 2L itself, not class 1. 'Elevated toxicity versus reduced toxicity' reads the number as toxicity, yet both carry the letter A, the lower-toxicity group. 'Toxic decomposition versus elevated thermal stability' is wrong because any halogenated refrigerant, A1 included, decomposes in a flame and gives off toxic products.

Correct answer: Reclaimed

Reclaimed refrigerant is used refrigerant that has been reprocessed to the AHRI 700 purity specification and verified by laboratory analysis, which is exactly what the reclaimer's report shows. 'Recovered' only means removed from a system and stored, in any condition; 'Recycled' means cleaned in the field by oil separation and filter-driers, with no analysis; 'Virgin' means newly manufactured product that has never been in a system.

Correct answer: Pressure governed by temperature

While any liquid is present, a cylinder sits at the saturation pressure for its temperature, so the reason is 'Pressure governed by temperature': the gauge reads the same at one-quarter full as at the limit, and only a scale shows when the fill reaches 80 percent of capacity by weight. 'Pressure governed by liquid level' is wrong because the reading does not climb as the liquid level rises; 'Pressure governed by container size' is wrong because saturation pressure is the same in a small or a large container at the same temperature; 'Pressure governed by vapor volume' is wrong because the vapor space stays at saturation pressure however small it becomes.

Correct answer: Repeated catalytic regeneration

Chlorine takes an oxygen atom from ozone, gives it up again in a second step and is left free to repeat the cycle, so the property described is 'Repeated catalytic regeneration'; one atom can destroy many thousands of ozone molecules. 'Gradual consumption' is wrong because a reactant is used up, even if slowly, and chlorine is not; 'Long-term atmospheric stability' describes the CFC molecule that carries the chlorine upward, not what the freed atom does there; 'Oxygen scavenging' is wrong because chlorine breaks ozone apart, and it does not block the formation of ozone by taking up oxygen.

Correct answer: Smaller ODP for R-22, a nonzero figure

R-22 is an HCFC: it still contains chlorine, but its hydrogen makes it break down sooner in the lower atmosphere, so the accurate statement is 'Smaller ODP for R-22, a nonzero figure' (about 0.05 against 1.0 for R-12). 'Smaller ODP for R-22, a figure of zero' gives R-22 the rating of an HFC, which has no chlorine; 'Smaller ODP for R-12, a nonzero figure' reverses the two, since the fully halogenated CFC is the more damaging; 'Smaller ODP for R-12, a figure of zero' reverses them and also treats a CFC as harmless to ozone.

Correct answer: Acceptable end uses and use conditions

Zero ODP is one property; acceptability is decided end use by end use. What a SNAP listing adds is 'Acceptable end uses and use conditions': a refrigerant can be acceptable in one application, restricted by use conditions in another and unacceptable in a third. 'Compatible oil type and seal materials' is wrong because SNAP reviews health and environmental risk, not compatibility with a given system; 'Minimum ozone and warming potential' is wrong because a listing means the overall risk is acceptable for that end use, weighing ozone depletion, global warming, toxicity and flammability together, not that the substitute scores lowest on any one measure; 'Recovery and evacuation level limits' is wrong because recovery and evacuation levels come from the Section 608 rules for each type of appliance.

Correct answer: Oxygen displacement by trapped vapor

The fans are what carry leaked vapor out of the room. With them stopped, the leaked refrigerant builds up and pushes out the air, so the danger is 'Oxygen displacement by trapped vapor', down to lethal oxygen levels: the asphyxiation hazard the oxygen-deprivation sensor is there to warn of. 'Phosgene formation in stagnant air' is wrong because decomposition needs a flame or a very hot surface, not still air; 'Rupture disc failure from overpressure' is wrong because a rupture disc responds to pressure inside the chiller, and a leak does not pressurize the room; 'Acid formation from moisture-laden air' describes contamination inside a system and is not what endangers a person walking in.

Correct answer: A reclaimer certificate of analysis showing it meets AHRI 700

Used refrigerant may be sold as equal to new only after an EPA-certified reclaimer has reprocessed it and chemical analysis has verified it against the AHRI 700 purity specification, so the buyer asks for 'A reclaimer certificate of analysis showing it meets AHRI 700'. 'A recovery machine test certificate showing it meets AHRI 740' covers the performance of a recovery or recycling machine, not the purity of this refrigerant; 'A recovery log signed by a Section 608 certified technician' shows only that the refrigerant was removed from a system; 'A copy of the Section 608 certification held by the seller' shows who may handle refrigerant and says nothing about what is in the cylinder.

Correct answer: ODP referenced to CFC-11, GWP referenced to carbon dioxide

Each metric has its own baseline with a value of 1: ozone depletion potential (ODP) is scaled to CFC-11 and global warming potential (GWP) is scaled to carbon dioxide, so 'ODP referenced to CFC-11, GWP referenced to carbon dioxide' is the correct contrast. 'ODP referenced to carbon dioxide, GWP referenced to CFC-11' swaps the two baselines; 'ODP referenced to CFC-11, GWP referenced to CFC-11' gives the warming scale the ozone reference; 'ODP referenced to carbon dioxide, GWP referenced to carbon dioxide' gives the ozone scale the warming reference, and carbon dioxide does not deplete ozone.

Correct answer: Phase-out goals enforced through the Clean Air Act

A treaty binds countries, not contractors. The Montreal Protocol sets international targets, and in the United States they become 'Phase-out goals enforced through the Clean Air Act': Title VI of the Act and the EPA regulations written under it are the domestic rules that carry the international targets, and they are what a contractor who vents refrigerant is penalized under. 'Phase-out goals enforced through the Pollution Prevention Act' names a law about reducing waste at the source, with no refrigerant rules; 'Phase-out goals enforced through the Toxic Substances Control Act' names the law for chemical reporting and testing; 'Phase-out goals enforced through the Hazardous Materials Transportation Act' names the law under which DOT regulates how refrigerant cylinders are shipped, and it does not regulate releases to the atmosphere.

Correct answer: How much stratospheric ozone the refrigerant destroys compared with CFC-11

Ozone depletion potential rates 'How much stratospheric ozone the refrigerant destroys compared with CFC-11', mass for mass, with CFC-11 given the baseline value of 1.0. 'How much heat the refrigerant traps compared with carbon dioxide' is global warming potential, the other metric; 'How much ground-level ozone the refrigerant generates compared with CFC-11' confuses the protective ozone layer with smog-forming ozone near the ground, which this value does not measure; 'How much time the refrigerant survives compared with carbon dioxide' describes atmospheric lifetime, which influences the value but is not what it quantifies.

Correct answer: Recovering the whole charge into an approved recovery cylinder before scrapping the unit

Section 608 requires the refrigerant to be removed before an appliance is disposed of, and it must go into a refillable cylinder approved for recovery, so the legal action is 'Recovering the whole charge into an approved recovery cylinder before scrapping the unit'. 'Recovering the whole charge into a disposable cylinder before scrapping the unit' is wrong because a disposable cylinder may never be refilled; 'Recovering the liquid alone into an approved recovery cylinder before scrapping the unit' is wrong because the vapor left behind would escape when the unit is cut up; 'Recovering the liquid alone into a disposable cylinder before scrapping the unit' makes both mistakes.

Correct answer: DOT-approved recovery cylinder within its five-year test date, filled to the 80 percent limit

A refillable recovery cylinder must be DOT-approved, must be hydrostatically retested every five years and must leave room for the liquid to expand, so the right container is 'DOT-approved recovery cylinder within its five-year test date, filled to the 80 percent limit'. 'DOT-approved disposable cylinder within its five-year test date, filled to the 80 percent limit' is wrong because a disposable cylinder, although built to a DOT specification, is made for a single use and may never be refilled with recovered refrigerant; 'DOT-approved recovery cylinder within its ten-year test date, filled to the 80 percent limit' doubles the retest interval, so the cylinder could be out of date; 'DOT-approved disposable cylinder within its ten-year test date, filled to the 80 percent limit' is wrong on both counts.

Correct answer: Four: Type I, Type II, Type III and Universal

Section 608 certification comes in "four: Type I, Type II, Type III and Universal". Type I covers small appliances, Type II high-pressure appliances and Type III low-pressure appliances, and Universal is held by a technician who has passed all three. "Three: Type I, Type II and Type III" leaves out Universal, the usual slip. "Four: the Core, Type I, Type II and Type III" counts the Core as a type, but the Core is the section everyone passes first and is not a certification by itself. "Five: Core, Type I, Type II, Type III and Universal" makes the same mistake while keeping Universal.

Correct answer: Ozone science and general regulatory knowledge

The Core is asked of everyone because it holds the "ozone science and general regulatory knowledge", together with the safety practice, that applies to refrigerant work on any equipment the technician goes on to service. "Small-appliance recovery methods and vacuum levels" is wrong because small appliances are the subject of Type I, a separate section, and Type I is not a prerequisite for Type II or Type III. "Refrigerant purchase and handling license" is wrong because passing the Core alone certifies no one; a technician is certified after also passing at least one type section. "Vehicle air conditioning service and repair" is wrong because motor vehicle air conditioning falls under Section 609, a separate certification that is part of no Section 608 type.

Correct answer: Stationary systems of Types I, II and III, excluding motor vehicles

A Universal certificate is earned by passing the Core and the three type sections, so it allows work on "stationary systems of Types I, II and III, excluding motor vehicles": small appliances, high-pressure appliances and low-pressure appliances. "Stationary systems of Types I, II and III, including motor vehicles" is wrong because motor vehicle air conditioning calls for a separate Section 609 certification. "Stationary systems of Types II and III, omitting Type I" is wrong because Universal includes small appliances. "Stationary systems of Types I and II, omitting Type III" is wrong because Universal includes low-pressure chillers.

Correct answer: A lifetime

Under EPA rules a Section 608 certification does not expire: it is valid for "a lifetime", and no renewal exam is set. "One year" is wrong because the certification is not an annual license that has to be renewed. "Five years" borrows the five-year interval for retesting refillable cylinders. "A decade" is wrong because the rules set no ten-year limit, or any other expiration date, on the certification.

Correct answer: Ozone-depleting substance

ODS stands for "ozone-depleting substance", the regulatory term for chemicals such as CFCs and HCFCs whose chlorine destroys stratospheric ozone. "Oxygen-depleting substance" confuses ozone depletion with the way a heavy refrigerant vapor can displace oxygen in a closed room. "Ozone-depleting standard" is wrong because ODS names the chemicals themselves and not a rule or a rating, and "oxygen-depleting standard" makes both mistakes.

Correct answer: R-12

R-12 is the CFC that was once the standard refrigerant in household refrigerators and in car air conditioning; its production ended with the other CFCs. R-22 is an HCFC used mainly in residential and commercial air conditioning. R-134a is the HFC that replaced R-12 in both of those uses, so it is the substitute and not the original. R-1234yf is an HFO that has in turn replaced R-134a in newer vehicles.

Correct answer: An HFC blend with zero ozone depletion potential and a significant global warming potential

R-410A is a mixture of two HFCs, R-32 and R-125, so it is "an HFC blend with zero ozone depletion potential and a significant global warming potential"; it contains no chlorine, and its warming effect is the reason HFCs are being phased down. "An HFO blend with zero ozone depletion potential and a significant global warming potential" names the wrong family: HFOs are the newer low-warming refrigerants, and R-410A contains none. "An HFC blend with a significant ozone depletion potential and zero global warming potential" has the two properties the wrong way round, and "an HFO blend with a significant ozone depletion potential and zero global warming potential" is wrong on both the family and the properties.

Correct answer: Hydrofluorocarbons (HFCs)

The 2016 Kigali Amendment added hydrofluorocarbons (HFCs) to the Montreal Protocol. HFCs do not deplete ozone, but many have a very high global warming potential, so the amendment set a worldwide schedule to phase down their production and consumption. Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) were already controlled by the original Protocol and its earlier amendments because they deplete ozone. Hydrofluoroolefins (HFOs) have very low global warming potential and are among the replacements, not the target.

Correct answer: Caps on yearly HFC production and import volumes

Under the AIM Act, the EPA allowance system sets caps on yearly HFC production and import volumes: allowances are allocated to companies and the total steps down over time. "Lists of acceptable HFC substitutes and end uses" describes SNAP, not the allowance system. "Limits on HFC leak rates and repair times" belong to the leak-repair provisions, and "certification of HFC buyers and technicians" describes the technician certification and sales restriction.

Correct answer: To reduce refrigerant releases through careful recovery and handling

Section 608 exists to reduce refrigerant releases through careful recovery and handling: the venting prohibition, recovery and recycling, reclamation, leak repair and technician certification all serve that aim. The goal to end ozone damage through refrigerant production and import bans belongs to the phaseout provisions of the Clean Air Act and the Montreal Protocol. The task to guide refrigerant choice through lists of uses and substitutes is the SNAP program under Section 612, and the job to limit refrigerant exposure through workplace rules and monitoring belongs to OSHA and the safety standards.

Correct answer: The pressure saturated refrigerant exerts at a given temperature

A pressure-temperature chart shows the pressure saturated refrigerant exerts at a given temperature: while liquid and vapor are present together, each temperature has one pressure, which lets a technician check the charge, spot noncondensables and help identify a refrigerant. The relationship holds only at saturation. "The pressure superheated refrigerant exerts at a given temperature" and "the temperature superheated refrigerant reaches at a given pressure" are not fixed, because vapor heated above saturation can be at many temperatures for one pressure. "The temperature subcooled refrigerant reaches at a given pressure" is not fixed either, since liquid can be cooled any amount below saturation; superheat and subcooling are found by comparing a measured temperature with the chart.

Correct answer: The refrigerant absorbs heat as it boils

In the evaporator "the refrigerant absorbs heat as it boils": the change from liquid to vapor takes up heat from the surrounding air, and that is what cools the space. "The refrigerant rejects heat as it boils" reverses the direction of heat flow. "The refrigerant absorbs heat as it condenses" names the wrong change of state, because condensing gives heat up. "The refrigerant rejects heat as it condenses" is true of the condenser, not the evaporator.

Correct answer: Polyolester oil

HFC systems such as R-410A commonly use polyolester oil (POE), because HFCs do not mix with the older oils and the oil would not return to the compressor. Mineral oil was the lubricant of CFC and HCFC systems and is not miscible with HFCs. Alkylbenzene oil is a synthetic used mainly with HCFC refrigerants and their blends. Polyalkylene glycol oil (PAG) is the lubricant of automotive R-134a systems, not of stationary R-410A equipment.

Correct answer: Poor compatibility of the original oil

The oil is changed because of the "poor compatibility of the original oil" with the new refrigerant: if the two do not mix, the oil does not return from the system and the compressor is starved of lubrication. "Corrosive reaction of the original oil" is wrong: acid forms where moisture or overheating is present, not because a refrigerant is changed. "Thermal breakdown of the original oil" is not the reason; miscibility is. "Reclamation of the original oil" confuses oil with refrigerant: reclamation applies to refrigerant.

Correct answer: Refrigerant type and weight

For refrigerant work the most useful nameplate data is the refrigerant type and weight: the factory charge tells the technician which refrigerant the system uses and how much it holds, which prevents cross-contamination and overcharging. The rated voltage and frequency and the fuse and breaker ratings are electrical data, needed for electrical service. The model and serial numbers identify the appliance for parts and records but say nothing about the charge.

Correct answer: A refrigerant mixture impossible to reclaim

Identification comes first because putting different refrigerants together can leave "a refrigerant mixture impossible to reclaim"; a contaminated mixture cannot be reused as it is and is costly to separate or must be destroyed. "A refrigerant mixture unlawful to transport" is wrong: a mixture can be shipped in a proper cylinder to a reclaimer or a destruction facility. "A recovery requiring an EPA waiver" is not a problem under any rule; an unidentified refrigerant is recovered like any other, into a cylinder of its own. Nor is "a recovery requiring a Universal technician" the concern; certification follows the type of appliance.

Correct answer: Confirm refrigerant purity

A refrigerant identifier is used to confirm refrigerant purity, showing before recovery whether the charge is the labeled refrigerant or has been mixed or contaminated; that protects the recovery machine and the clean recovery cylinders. To identify refrigerant leaks a technician uses an electronic leak detector or soap solution. To measure vacuum depth takes a micron gauge, and to measure oil acidity takes an acid test kit.

Correct answer: Removal of residual air and moisture

A recovery cylinder is evacuated before use for the removal of residual air and moisture; noncondensables and water left inside would contaminate the recovered charge and count against it at reclamation. A vacuum does not achieve the removal of residual acids and sludge, because those do not boil off. Evacuation brings no "change of capacity and fill limit": the limit stays at 80 percent by weight. Nor does it bring a "change of retest date and cylinder rating"; the retest date and the DOT rating of a cylinder are fixed by its test record.

Correct answer: Dry nitrogen

Dry nitrogen is the standard leak-test gas: it is inert, free of moisture and harmless to the ozone layer, so releasing it afterwards is not prohibited. Pure oxygen must never be used, because it can react explosively with oil. Compressed air carries moisture and oxygen into the system. Refrigerant vapor used as the test gas would be released when the test ends, which is exactly what the rules are meant to stop.

Correct answer: Explosive combustion of oil and contaminants

Pure oxygen is never used for a pressure test because of the "explosive combustion of oil and contaminants"; oil under oxygen pressure can ignite without a flame. "Gradual formation of acid and sludge" describes the slow damage that moisture and air do, not the immediate danger. "Air displacement and asphyxiation of workers" is the hazard of nitrogen and refrigerant vapor; oxygen does not suffocate. "Toxic and corrosive breakdown of refrigerant" is what an open flame or a very hot surface causes.

Correct answer: Air and moisture removal

Pulling a vacuum before charging dehydrates the system: the result is "air and moisture removal", and moisture left behind would form acids and ice and cause corrosion and poor performance. "Acid and sludge removal" is wrong because those do not boil off under a vacuum and are taken out by filter-driers and an oil change. "Carbon and scale removal" is wrong for the same reason. "Dirt and filings removal" is wrong because solids are caught by strainers and filters, not by a vacuum pump.

Correct answer: Form corrosive acids and freeze in the expansion device

Moisture can form corrosive acids and freeze in the expansion device: it reacts with the refrigerant and oil, and ice at the metering (expansion) device blocks the flow. That is why systems are evacuated and fitted with a drier. To collect in the condenser and raise the head pressure is what air and other noncondensables do. To dilute the oil and wash out the compressor bearings is the damage done by liquid refrigerant flooding back. To coat the evaporator tubes and reduce the suction pressure describes oil logging.

Correct answer: Evacuation to the applicable regulatory level

For a major repair the rule is "evacuation to the applicable regulatory level": the regulations set a required recovery level by appliance type, refrigerant and charge, so that very little refrigerant is left to escape when the system is opened. "Recovery to atmospheric pressure" is the allowance for a repair that is not major or for a system that cannot hold a vacuum. "Evacuation to the specified dehydration level" describes the deep vacuum pulled before charging, not the recovery requirement. "Recovery to a liquid receiver" describes a pump-down, which isolates the charge but is not the general rule.

Correct answer: Active uses a self-contained machine; passive uses the appliance itself

The methods differ in what moves the refrigerant: "active uses a self-contained machine; passive uses the appliance itself". Active recovery equipment has its own compressor or pump, while passive, system-dependent recovery relies on the appliance compressor or on the pressure inside the appliance to push refrigerant into the cylinder. "Active uses the appliance itself; passive uses a self-contained machine" swaps the two. "Active recovers liquid refrigerant; passive recovers vapor refrigerant" and "active recovers vapor refrigerant; passive recovers liquid refrigerant" are both wrong, because either method can move liquid or vapor.

Correct answer: Contaminated refrigerant restored to new product purity

Refrigerant that changes owners must be reclaimed because it may be contaminated; the aim is "contaminated refrigerant restored to new product purity": a reclaimer reprocesses it and has it analyzed against AHRI Standard 700 before resale. "Mixed refrigerant converted to an approved replacement blend" is wrong, since reclaiming does not make a new refrigerant out of a mix. "Recovered refrigerant reported to the EPA" mistakes a purity requirement for a paperwork one. "Recycled refrigerant subjected to an identical cleaning off site" treats the two as the same step, but recycling is a basic cleanup with no purity standard to meet, and recycled refrigerant may go back only into equipment of the same owner.

Correct answer: AHRI Standard 700

AHRI Standard 700 is the purity specification that reclaimed refrigerant must meet, confirmed by laboratory analysis, before it is sold as equal to new product. ASHRAE Standard 15 covers the safe design and installation of refrigeration systems, including equipment rooms. ASHRAE Standard 34 gives refrigerants their designations and safety groups. AHRI Standard 740 rates the performance of recovery and recycling equipment, not the purity of the refrigerant.

Correct answer: A signed statement that records the transfer and final disposition

Recovered refrigerant or a sealed appliance sent for reclamation or disposal travels with a signed statement that records the transfer and final disposition, so the quantity and its handling can be traced and verified. A safety data sheet that lists the hazards and precautions is hazard information, not a tracking record. A service record that shows the leak and repair dates belongs to the leak-repair requirements for an operating appliance. A laboratory report that certifies the purity and moisture content is produced by the reclaimer after processing, not sent in with the shipment.

Correct answer: Total recovery to leave the cylinder empty

Before a disposable cylinder is discarded the rule is "total recovery to leave the cylinder empty"; only an empty cylinder may be scrapped or recycled as metal. "Direct release to leave the cylinder empty" describes venting, which is prohibited whatever the size of the container. "Hauler pickup in the sealed cylinder" would send pressurized refrigerant to a scrap yard. "Supplier return in the sealed cylinder" describes a returnable, refillable cylinder, not a disposable one.

Correct answer: They are built for single use and lack safety features for repeated refilling

Disposable cylinders are never refilled because "they are built for single use and lack safety features for repeated refilling": they are thin-walled, are not retested, and are not made for repeated pressurization, so recovered refrigerant goes into a refillable recovery cylinder that is retested on schedule. "They are built for vapor service and lack strength for liquid refrigerant" is wrong because disposable cylinders hold liquid refrigerant and deliver it when inverted. "They are built for supplier return and lack a connection for field recharging" is wrong because returnable cylinders are a different, refillable design, and a disposable cylinder is scrapped once it is empty. "They are built for retail sale and lack a valve that reseals afterward" is wrong because the valve is opened and closed again throughout normal use.

Correct answer: Frostbite

Liquid refrigerant on bare skin causes frostbite: it evaporates so fast that it pulls heat out of the tissue and freezes it, which is why gloves and eye protection are worn. Dermatitis is the slow irritation that comes from repeated contact with oils and solvents. A chemical burn comes from acid, such as the acidic oil of a burned-out compressor. A thermal burn comes from hot surfaces such as a discharge line or a brazed joint.

Correct answer: Safety glasses or goggles rated for chemicals and impact

The eyes are protected by safety glasses or goggles rated for chemicals and impact, because a spray of liquid refrigerant can freeze eye tissue. A welding helmet or face shield rated for sparks and flame is made for brazing and welding and is not worn for gauge work. Prescription lenses or sunglasses rated for sun and glare have no side protection and no splash rating. A dust mask or respirator rated for mist and vapor protects the lungs and leaves the eyes uncovered.

Correct answer: Passing the probe near joints to sense escaping vapor

An electronic leak detector is used by passing the probe near joints to sense escaping vapor; moved slowly, it responds to very small amounts of refrigerant. The other three are real leak checks that use no electronic detector: a bubble test means wiping soap solution on fittings to watch bubbles form, a dye test means injecting dye into the oil to stain leaks, and a standing vacuum test means pulling a deep vacuum to watch its gauge pressure rise.

Correct answer: Topping off lets new refrigerant escape, which defeats the emission-reduction goal

Leak repair is stressed because "topping off lets new refrigerant escape, which defeats the emission-reduction goal": every recharge of a leaking system replaces refrigerant that has gone to the atmosphere and will go there again. "Topping off introduces moisture into the refrigerant, which damages the compressor" is not the reason, since a careful recharge introduces no moisture. "Topping off adds too much refrigerant, which floods the compressor with liquid" describes overcharging, not what happens when a lost charge is replaced. "Topping off the refrigerant is a major repair, which needs full evacuation" is wrong because a major repair means removing a compressor, condenser, evaporator or auxiliary heat exchanger coil.

Correct answer: Asphyxiation

When vapor pushes the oxygen out of a space the hazard is asphyxiation: most refrigerants are heavier than air, settle in low or enclosed areas, and a worker can pass out without warning. Cardiac arrhythmia is a different inhalation hazard, caused by the refrigerant itself sensitizing the heart at high concentrations. Phosgene poisoning and hydrofluoric acid burns come from the breakdown products formed when refrigerant meets an open flame or a very hot surface, not from a lack of oxygen.

Correct answer: Low toxicity with zero flame propagation

In an ASHRAE Standard 34 safety group the letter gives toxicity and the number gives flammability, so A1 means low toxicity with zero flame propagation (class A is the lower-toxicity class, and class 1 shows no flame propagation), the safest group to handle, although the vapor can still displace oxygen. Low toxicity with high flammability is group A3, which includes propane. Elevated toxicity with zero flame propagation is group B1, which includes R-123. Elevated toxicity with high flammability is group B3.

Correct answer: Ignition source control, given mild flammability

The number in a safety group gives flammability, and 2L means lower flammability with a slow burning velocity, so the added precaution is "ignition source control, given mild flammability": ignition sources are kept away from the work. "Ignition source control, given elevated toxicity" gives the right precaution for the wrong reason: toxicity is shown by the letter, and A means lower toxicity. "Canister respirator use, given elevated toxicity" is wrong on both counts. "Canister respirator use, given mild flammability" has the right reason, but a respirator does nothing about the risk of ignition.

Correct answer: Ozone depletion or climate change

Venting is prohibited because of "ozone depletion or climate change": CFCs and HCFCs destroy stratospheric ozone, and those refrigerants and the HFCs are strong greenhouse gases. "Smog or acid rain at ground level" confuses the ozone layer with ground-level ozone pollution, which comes from other emissions. "Soil or groundwater contamination" is wrong because a refrigerant leaves as a gas. "Open-air ignition or explosion" is wrong because the common refrigerants covered by the prohibition are nonflammable or only mildly flammable.

Correct answer: Acceptable substitutes by end use, with their use conditions

The Significant New Alternatives Policy (SNAP) program reviews substitutes and publishes lists showing "acceptable substitutes by end use, with their use conditions", so a technician can choose a replacement that is legal for the application. The lists do not show "available substitutes by reclaimer, with their purity ratings"; reclaimers are certified under Section 608 and purity is set by AHRI Standard 700. They do not show "covered substitutes by certification type, with their charge limits"; certification types follow the kind of appliance, not a list of refrigerants. Nor do they show "recovered substitutes by vacuum level, with their recovery units"; those levels are in the Section 608 evacuation requirements.

Correct answer: SNAP acceptable use listing covering that application

A substitute that cools is not automatically legal: the technician must confirm a "SNAP acceptable use listing covering that application", because the EPA reviews each substitute by end use and may attach use conditions. An "ASHRAE standard safety listing covering that application" is wrong because ASHRAE assigns safety groups and does not approve substitutes for an end use. A "DOT cylinder transport listing covering that application" is wrong because DOT rules govern cylinders and transport. An "OSHA industrial safety listing covering that application" is wrong because OSHA sets workplace safety rules and keeps no list of acceptable substitutes.

Correct answer: Scale weighing, up to 80 percent of rated capacity

The reliable method is "scale weighing, up to 80 percent of rated capacity": only weight shows how much liquid is in the cylinder, and the remaining space lets the liquid expand as it warms. "Scale weighing, up to 90 percent of rated capacity" uses the right method with the wrong limit; 90 percent is a Type I recovery figure, not a fill limit. "Gauge readings, up to 80 percent of rated pressure" and "gauge readings, up to 90 percent of rated pressure" cannot work, because the pressure in a cylinder that holds liquid depends on temperature and stays almost the same from nearly empty to dangerously full.

Correct answer: 5 pounds or less of refrigerant

A small appliance is fully manufactured, charged and hermetically sealed in a factory and holds '5 pounds or less of refrigerant'; both conditions must be met for Type I to apply. '15 pounds or less of refrigerant' and '50 pounds or less of refrigerant' borrow charge thresholds from other refrigerant rules, such as the 50-pound trigger for leak repair on larger appliances, and '200 pounds or less of refrigerant' borrows the charge size that sets the required evacuation level for high-pressure appliances.

Correct answer: Factory manufacture, charging and hermetic sealing

The definition has two parts: a charge of 5 pounds or less, and a unit that arrives complete, fully manufactured, charged and hermetically sealed at the factory, so the other condition is 'Factory manufacture, charging and hermetic sealing'. 'Residential design, labeling and consumer sale' is wrong because the definition does not depend on where the unit is used; vending machines and commercial ice makers can qualify. 'Job-site delivery, installation and refrigerant charging' describes field-charged equipment, which is exactly what the definition excludes. 'High-pressure design, testing and performance rating' is wrong because the definition names no pressure class or refrigerant.

Correct answer: Field assembly and field charging

A small appliance must be fully manufactured, charged and hermetically sealed at the factory, so the disqualifying fact is 'Field assembly and field charging' at the installation site. 'Commercial sale and restaurant installation' does not matter, because the definition ignores where the unit operates; 'High-pressure design and construction' does not matter, because the definition names no pressure class, and room air conditioners charged with R-410A are small appliances; 'Shop leak repair and recharging' does not matter, because a later repair does not change how the unit was originally built and sealed.

Correct answer: 90 percent

With a working compressor to help move the refrigerant, the technician must recover 90 percent of the charge from a small appliance. '80 percent' is the figure for a compressor that does not operate; '85 percent' splits the difference between the two real levels and is not in the rule; '95 percent' overshoots the higher level, and no Type I requirement is set that high.

Correct answer: 80 percent

Without a working compressor it is harder to draw the refrigerant out, so the requirement for a small appliance drops to 80 percent of the charge. '90 percent' is the figure that applies when the compressor does operate; '70 percent' undershoots the lower level and would leave too much refrigerant in the unit; '95 percent' is above even the working-compressor level and is not a Type I figure.

Correct answer: 90 percent

The refrigerator's compressor still runs, so the higher Type I level applies and the technician must remove at least '90 percent' of the charge. '80 percent' is the level for a small appliance whose compressor does not operate; '85 percent' sits between the two real levels and is not in the rule; '75 percent' is below even the non-working level and would leave too much refrigerant behind.

Correct answer: Compliant: a failed compressor lowers the minimum

Type I has two levels: 90 percent with an operating compressor and 80 percent without one. The compressor here is seized, so the 82 percent recovered meets the standard: 'Compliant: a failed compressor lowers the minimum'. 'Compliant: a failed compressor waives the minimum' reaches the right verdict for a false reason, since a recovery level still applies when the compressor is dead; 'Noncompliant: a failed compressor raises the minimum' assigns the working-compressor figure to the wrong condition; 'Noncompliant: a failed compressor leaves the minimum unchanged' ignores the lower level the rule allows for a dead compressor.

Correct answer: 90 percent with a working compressor, 80 percent without

Recovery equipment for small appliances made after November 15, 1993 must be certified to the recovery rates set for that newer equipment: '90 percent with a working compressor, 80 percent without'. '80 percent with a working compressor, 90 percent without' reverses the two conditions, and a working compressor is what makes the higher figure achievable; '80 percent with or without a working compressor' is the single level that applies to equipment made before that date; '90 percent with or without a working compressor' drops the lower level the rule allows when the compressor cannot help.

Correct answer: Newer efficiency standards for later equipment

November 15, 1993 is the cutoff that decides which recovery-equipment efficiency standard applies: 'Newer efficiency standards for later equipment' (90 percent with a working compressor and 80 percent without), while equipment made earlier stays under the standard it was built to. 'Mandatory retirement for earlier equipment' is wrong because older equipment may stay in service under its earlier standard; 'Mandatory upgrades for earlier equipment' is wrong for the same reason, since no retrofit is required; 'Self-contained design rule for later equipment' is wrong because system-dependent equipment is still permitted on small appliances.

Correct answer: It relies on the appliance compressor or internal pressure to push the refrigerant out

System-dependent equipment has no means of its own to move refrigerant: 'It relies on the appliance compressor or internal pressure to push the refrigerant out' and into the recovery container. 'It relies on a compressor or condenser inside the recovery machine to draw the refrigerant out' is the definition of self-contained (active) equipment; 'It relies on deep vacuum pumps or dry nitrogen to drive the refrigerant out' is wrong because a vacuum pump is for dehydration after recovery and nitrogen is not used to push a charge out; 'It relies on liquid pumps or push-pull hose sets to move the refrigerant out' describes liquid-transfer methods used with active equipment on large systems.

Correct answer: Small appliances

Passive equipment depends on the appliance's own compressor or pressure to move the charge, so it is accepted for 'Small appliances', the factory-sealed units with a few pounds of refrigerant. 'High-pressure appliances' such as split systems and rooftop units are not a class the rule singles out: passive equipment is barred on any appliance holding more than 15 pounds; 'Low-pressure appliances' such as centrifugal chillers are recovered with active equipment into deep vacuum; 'MVAC-like appliances' such as farm and off-road vehicle air conditioners are serviced with the recovery equipment approved for motor vehicle systems, not with passive devices.

Correct answer: Use restricted to small appliances, excluding larger equipment

A 70-pound rooftop system is far outside the small-appliance class, and the rule for a system-dependent device is 'Use restricted to small appliances, excluding larger equipment'; the job calls for self-contained (active) recovery equipment. 'Use restricted to large chillers, excluding rooftop units' is wrong because chillers are recovered with active equipment; 'Use restricted to household models, excluding commercial units' is wrong because the limit follows the size and type of appliance, not who owns it; 'Use restricted to failed compressors, excluding working ones' is wrong because passive recovery works best when the appliance compressor still runs.

Correct answer: Built-in pump and compressor for unaided removal

The difference is where the moving force comes from: self-contained equipment has a 'Built-in pump and compressor for unaided removal', so it pulls the refrigerant out without the appliance's help, whether or not the appliance compressor runs. 'Built-in hoses and valves for passive transfer' describes system-dependent recovery, where the appliance itself pushes the charge into the recovery container; 'Built-in filter and drier for on-site reclaiming' is wrong because reclaiming to AHRI 700 purity is done by a certified reclaimer, not by a recovery machine; 'Built-in tank and scale for cylinder-free recovery' is wrong because recovered refrigerant still goes into an approved recovery cylinder.

Correct answer: Self-contained (active) recovery equipment

With a dead compressor and a restriction in the system, nothing inside the appliance can move the charge, so the job calls for 'Self-contained (active) recovery equipment', which has its own compressor. 'System-dependent (passive) recovery equipment' relies on the appliance compressor or pressure, the very things this unit lacks; 'Push-pull (liquid transfer) recovery equipment' is a method for moving bulk liquid out of large systems and is not used on a charge of a few pounds; 'Pump-out (chiller-attached) recovery equipment' is a unit permanently attached to a large chiller, not something carried to a small appliance.

Correct answer: A household refrigerator

A household refrigerator is built, charged and hermetically sealed at the factory and holds well under 5 pounds of refrigerant, which is the small-appliance definition. 'A split-system heat pump' is piped and charged in the field, so it is Type II high-pressure equipment whatever its size; 'A walk-in freezer system' is likewise field-assembled with a remote condensing unit and falls under Type II; 'A low-pressure chiller' is Type III equipment.

Correct answer: A supermarket rack refrigeration system

A supermarket rack refrigeration system is assembled and charged in the field and holds far more than 5 pounds of refrigerant (60 pounds would be a small one), so it is not a small appliance; it is Type II equipment. 'A packaged terminal air conditioner', 'A self-contained undercounter ice maker' and 'A plug-in drinking water cooler' are all built, charged and hermetically sealed at the factory with 5 pounds or less of refrigerant, so each one is a Type I small appliance.

Correct answer: Type I, because a PTAC is a factory-sealed small appliance

A PTAC is built, charged and hermetically sealed at the factory and holds 5 pounds or less, so the answer is 'Type I, because a PTAC is a factory-sealed small appliance'. 'Type II, because a PTAC runs on high-pressure refrigerants' is the tempting slip: the refrigerant is a high-pressure one, but a factory-sealed unit of this size is classed by the small-appliance definition, not by pressure. 'Type III, because a PTAC runs on low-pressure refrigerants' is wrong because low-pressure refrigerants are found in centrifugal chillers. 'Type II, because a PTAC is a unit in a commercial building' is wrong because commercial use does not set the category; the small-appliance definition does.

Correct answer: Section 609

Section 609 of the Clean Air Act covers the servicing of motor vehicle air conditioners and has its own technician certification, separate from Section 608. 'Section 612' is the Significant New Alternatives Policy (SNAP) program for substitutes; 'Section 611' is the labeling requirement for products made with or containing ozone-depleting substances; 'Section 605' is the phase-out schedule for class II substances, the HCFCs.

Correct answer: Decline, because car air conditioners require Section 609 certification

Section 608 covers stationary equipment; motor vehicle air conditioners are serviced under a separate program, so the technician should 'Decline, because car air conditioners require Section 609 certification'. 'Proceed, because Type I certification covers factory-sealed car air conditioners' is wrong because the small-appliance class does not include vehicle systems, however small or well sealed; 'Proceed, because Section 608 certification includes car air conditioners' is wrong because no Section 608 type extends to them; 'Decline, because car air conditioners require Type II certification' reaches the right decision for a false reason, since Type II is a Section 608 credential for stationary high-pressure equipment.

Correct answer: Section 608 covers stationary factory-sealed units, and Section 609 covers motor vehicle air conditioners

The two programs divide by the kind of equipment: 'Section 608 covers stationary factory-sealed units, and Section 609 covers motor vehicle air conditioners', meaning the air-conditioning systems of cars and light trucks. 'Section 609 covers stationary factory-sealed units, and Section 608 covers motor vehicle air conditioners' reverses the two sections. 'Section 608 covers ozone-depleting refrigerants, and Section 609 covers HFC refrigerants' draws the line by refrigerant, a common slip because cars moved to R-134a early, but both sections apply whatever the refrigerant; 'Section 609 covers ozone-depleting refrigerants, and Section 608 covers HFC refrigerants' makes the same mistake with the sections reversed.

Correct answer: A Type I small appliance

Classification follows how the unit was built and how much it holds, not the refrigerant inside it. A window air conditioner that was charged and sealed at the factory with 5 pounds or less is 'a Type I small appliance'. R-410A is a high-pressure refrigerant, which makes 'a Type II high-pressure appliance' the tempting slip, but Type II covers high-pressure equipment that is not a small appliance. 'A Type III low-pressure appliance' is a chiller on a refrigerant such as R-11 or R-123. 'A Section 609 unit in a motor vehicle' is a car or truck air conditioner, which a window unit is not.

Correct answer: Operational appliance compressor

The 90 percent level goes with an 'operational appliance compressor', because a compressor that runs helps push the charge out. An 'inoperative appliance compressor' is the condition for the 80 percent level. 'Passive recovery method' and 'active recovery method' are not the test: the level follows the condition of the compressor, never whether the recovery device has a pump of its own.

Correct answer: Type I

A water cooler that was hermetically sealed at the factory with 2 pounds of refrigerant meets both tests for a small appliance (factory-sealed, 5 pounds or less), so Type I covers its service. Type II is for high-pressure appliances that are not small appliances, such as split systems and commercial refrigeration. Type III is for low-pressure appliances such as centrifugal chillers. Section 609 is the separate certification for motor vehicle air conditioners.

Correct answer: Recovery of the applicable percentage

System-dependent recovery is held to the same small-appliance levels as any other method, so what the rule asks for is 'recovery of the applicable percentage' (90 percent with a running compressor, 80 percent without), even though the device has no pump. 'Recovery of the liquid portion alone' leaves vapor behind that the rule counts as part of the charge. 'Evacuation to the Type III chiller level' borrows 25 mm Hg absolute, the level set for low-pressure chillers. 'Evacuation to the deep dehydration level' borrows the 500-micron target used to dry a system, which is not a recovery level.

Correct answer: Independent built-in compressor

Active, or self-contained, equipment is recognized by an 'independent built-in compressor' that draws the refrigerant out without help from the appliance. The other three are marks of system-dependent (passive) recovery, which has no pump and leans on the appliance: a 'functional appliance compressor' pumps the charge out itself, a 'non-pressurized recovery bag' fills from the pressure of the charge, and a 'chilled recovery cylinder' draws refrigerant across by a pressure difference instead of a pump.

Correct answer: Excluded: built and charged outside the factory

A small appliance must pass two tests: manufactured, charged and hermetically sealed at the factory, and 5 pounds or less. This unit fails the first, so the answer is 'excluded: built and charged outside the factory'. 'Qualifies: charge size alone decides' applies only the charge test. 'Qualifies: charged and sealed by the installers' erases the very distinction the definition draws, since sealing a system on site is not factory sealing. 'Excluded: rooftop equipment belongs to Type II' reaches the right verdict for the wrong reason, because where a unit is mounted never decides whether it is a small appliance.

Correct answer: Window air conditioner, household refrigerator, water cooler

Every member of 'window air conditioner, household refrigerator, water cooler' is charged and sealed at the factory with 5 pounds or less, so the whole list is Type I. Each other list hides one outsider. In 'beverage cooler, dehumidifier, passenger car air conditioner' the car air conditioner belongs to Section 609. In 'vending machine, wine cooler, split-system air conditioner' the split system is joined and charged in the field, which makes it Type II. In 'room air conditioner, chest freezer, walk-in cooler' the walk-in cooler is a field-built refrigeration system, also Type II.

Correct answer: Noncompliant: an operable compressor raises the minimum

A weak compressor that still runs counts as an operating compressor, and when the compressor operates the minimum is 90 percent, so 84 percent falls short: 'noncompliant: an operable compressor raises the minimum'. 'Compliant: a weak compressor counts as inoperative' is wrong because the 80 percent level is for a compressor that does not run at all. 'Compliant: passive recovery carries the reduced minimum' is wrong because the level follows the condition of the compressor, not the kind of recovery device. 'Noncompliant: sealed units require full recovery' overstates the rule; no small-appliance level asks for the whole charge.

Correct answer: Equipment outside the small-appliance class and unreliable passive recovery

The reason is 'equipment outside the small-appliance class and unreliable passive recovery'. These systems are not small appliances, and system-dependent recovery leans on the appliance to move the refrigerant, which suits a small sealed charge and cannot be counted on to reach the set levels on a large system. 'Blended refrigerant charges and fractionation with passive recovery' is wrong because the rule does not turn on the kind of refrigerant. 'Sub-atmospheric pressures and air leakage with passive recovery' describes low-pressure chillers, not high-pressure systems. 'The strict deep-vacuum dehydration standards and inadequate passive recovery' confuses the 500-micron drying target with a recovery level.

Correct answer: Type I

A vending machine that is hermetically sealed and holds 3 pounds is a factory-sealed unit with 5 pounds or less, which is the definition of a small appliance, so Type I applies. Type II covers high-pressure appliances that are not small appliances. Type III covers low-pressure appliances such as chillers. Section 609 is the motor vehicle air-conditioning certification and has nothing to do with stationary equipment.

Correct answer: Inoperative compressor

The 80 percent level applies with an 'inoperative compressor', because a dead compressor cannot help push the charge out. A 'working compressor' is the 90 percent case. A 'self-contained recovery unit' and a 'system-dependent recovery unit' do not lower the level, since the kind of recovery machine does not set the percentage.

Correct answer: Earlier standard for older recovery units

Recovery equipment is judged by the rule that applied when it was made, so a unit built before November 15, 1993 falls under the 'earlier standard for older recovery units', the one in effect when it was built. The 'current standard for newer recovery units' is the 90 or 80 percent rule for equipment made on or after that date. The 'current standard for newer appliances' and the 'earlier standard for older appliances' both look at the wrong machine: the date that matters is the date the recovery unit was made, not the age of the appliance it is used on.

Correct answer: Weak driving force and incomplete recovery

Passive recovery has no pump, so it depends on the appliance for its driving force, and a failed compressor supplies very little, which leaves recovery slow or short of the mark: 'weak driving force and incomplete recovery'. 'Missing compressor suction and high-side-only recovery' is backward, since a dead compressor is the case where both the high and low sides should be accessed. 'Added safety hazards and prohibited recovery' is wrong because the method stays legal; it is simply less effective. 'Overly rapid recovery and excessive oil loss' is the opposite problem, one that belongs to fast recovery with a powerful machine.

Correct answer: Type I

A dehumidifier that is factory-sealed with under 5 pounds is a small appliance, so Type I is the least a technician needs. Universal would also allow the work, but it combines Type I, Type II and Type III and is more than the minimum asked for. Type II covers high-pressure appliances that are not small appliances, and Type III covers low-pressure appliances.

Correct answer: 90 percent

With a working compressor the small-appliance minimum is 90 percent of the charge, so 88 percent falls short. 80 percent is the figure for a compressor that does not run, and 88 percent would have met it. 75 percent and 100 percent are not Type I levels at all: the rule sets nothing below 80 percent and never asks for more than 90 percent.

Correct answer: Lack of an internal pump

System-dependent equipment is defined by what it is missing: 'lack of an internal pump', which leaves it dependent on the appliance compressor or the pressure of the charge to move the refrigerant. 'Presence of an internal pump' is the mark of self-contained equipment. 'Presence of a recovery container' does not separate the two, because both kinds move the charge into a container. 'Lack of a recovery container' is wrong because passive recovery still collects the refrigerant in a bag or cylinder.

Correct answer: Factory seal and 5-pound maximum charge

Two facts define a small appliance, and the ice maker has both: 'factory seal and 5-pound maximum charge'. 'Domestic use and 5-pound maximum charge' gets the charge right but swaps the factory-seal test for household use, which the definition never mentions (commercial ice makers and vending machines qualify too). 'Factory seal and wall-outlet power' keeps the seal but replaces the charge limit with the power supply. 'Domestic use and wall-outlet power' names neither of the two tests.

Correct answer: Failed appliance compressor

Self-contained equipment brings its own pump, so it earns its keep with a 'failed appliance compressor' that is dead and cannot help move the refrigerant. A 'fully working appliance compressor' is the case where passive recovery works well. A 'fully leaked refrigerant charge' leaves nothing to recover. An 'unusually small refrigerant charge' does not call for a pump either; small charges are what passive devices handle.

Correct answer: Excluded: charge exceeds the small-appliance limit

Both tests must be met, and a 6-pound charge fails one of them, the 5-pound limit: 'excluded: charge exceeds the small-appliance limit'. 'Qualifies: factory sealing is the sole small-appliance test' applies only the factory-seal test. 'Qualifies: charge satisfies the small-appliance limit' gets the figure wrong; the limit is 5 pounds or less, and 6 pounds is over it. 'Excluded: household use is the sole small-appliance test' gives a wrong reason, since commercial units such as vending machines and water coolers are small appliances.

Correct answer: System-dependent recovery

System-dependent recovery, also called passive recovery, uses the compressor or the pressure of the appliance instead of a pump in the recovery device, and it is the method tied to small appliances. Self-contained recovery, also called active recovery, is used on equipment of every size. Push-pull liquid recovery is a technique for moving large liquid charges out of big systems. Self-contained vapor recovery is the ordinary way a recovery machine finishes a job on any appliance.

Correct answer: Compliant: recovery surpasses the working-compressor minimum

With a working compressor the Type I minimum is 90 percent, and 91 percent is above it: 'compliant: recovery surpasses the working-compressor minimum'. 'Noncompliant: recovery misses the working-compressor minimum' has the comparison backward, since 91 is more than 90. 'Compliant: beverage coolers carry a reduced minimum' reaches the right verdict from a rule that does not exist; the kind of product does not change the level, and the figure that applies here is the one for a working compressor. 'Noncompliant: beverage coolers require complete recovery' invents a level above 90 percent; the Type I rule never asks for the whole charge.

Correct answer: Harder recovery without compressor assistance

The lower figure reflects a practical limit: 'harder recovery without compressor assistance'. A compressor that cannot run no longer helps push the charge out, so the same level is more difficult to reach and the minimum drops from 90 to 80 percent. 'Smaller refrigerant charge without system operation' is wrong because a failed compressor does not mean the charge has escaped. 'Contaminated refrigerant charge without reuse value' mixes up recovery with reuse; contaminated refrigerant must still be recovered. 'Scrapped compressors without strict recovery rules' is wrong because the same levels apply at disposal.

Correct answer: Charge-percentage recovery levels

A sealed unit with 1 pound of refrigerant is a small appliance however small the charge, so it follows the Type I rules, the 'charge-percentage recovery levels': 90 percent with a running compressor, 80 percent without. 'Medium-pressure evacuation levels' are the Type II inches-of-mercury vacuum levels for appliances that are not small appliances. 'Low-pressure evacuation levels' means the Type III figure, 25 mm Hg absolute, for low-pressure chillers. 'Leak-rate percentage levels' are the annual leak rates that trigger repairs on larger comfort-cooling and commercial refrigeration systems, not recovery levels.

Correct answer: Outside Section 608, covered by Section 609

Size and sealing do not decide this one. Motor vehicle air conditioners are excluded from Section 608 and covered under Section 609, a separate EPA program with its own technician certification: 'outside Section 608, covered by Section 609'. 'Outside Section 608, covered by Section 612' names the wrong section, because Section 612 is the SNAP program that reviews substitute refrigerants. 'Inside Section 608, covered by Type II' is wrong because Type II is for stationary high-pressure appliances. 'Inside Section 608, covered by Universal' is wrong because Universal only combines Type I, Type II and Type III, none of which reaches vehicle systems.

Correct answer: Factory-charged, hermetically sealed unit holding 5 pounds maximum

The EPA definition joins two conditions, a product fully assembled, charged and hermetically sealed at the factory and a charge of 5 pounds or less: 'factory-charged, hermetically sealed unit holding 5 pounds maximum'. 'Factory-charged, hermetically sealed unit holding 15 pounds maximum' keeps the factory seal but borrows 15 pounds from another rule. 'Field-charged, hermetically sealed unit holding 5 pounds maximum' keeps the charge limit but drops the factory condition, so a small system charged on site is not a small appliance. 'Field-charged, hermetically sealed unit holding 15 pounds maximum' misses both conditions.

Correct answer: Self-contained recovery equipment

With a dead compressor the appliance cannot help move its own charge, so self-contained recovery equipment (active equipment, which has its own pump) is the approach most likely to reach the required 80 percent. System-dependent recovery equipment is passive and relies on the very compressor that has failed. Push-pull liquid recovery equipment is set up for large liquid charges, not for a sealed system holding a few pounds. Motor vehicle recovery equipment is certified under Section 609 for cars, not for small appliances.

Correct answer: Factory seal, 5-pound maximum charge: Type I small appliance

The two facts that settle it are the factory seal and the charge: 'factory seal, 5-pound maximum charge: Type I small appliance'. 'Domestic use, 5-pound maximum charge: Type I small appliance' lands on the right type but relies on household use, which is not part of the definition. 'Factory seal, high-pressure refrigerant: Type II appliance' and 'comfort use, high-pressure refrigerant: Type II appliance' both let the refrigerant decide, and a sealed unit of 5 pounds or less is Type I whatever refrigerant it holds.

Correct answer: November 15, 1993

November 15, 1993 is the manufacturing date that separates older recovery equipment from equipment that must be certified to the current small-appliance rates (90 percent with a working compressor, 80 percent without). July 1, 1992 is the date the venting prohibition took effect. November 14, 1994 is the date technician certification became mandatory. January 1, 1996 is the date CFC production ended in the United States.

Correct answer: Uses the appliance compressor or pressure; restricted to small appliances

Passive recovery has no pump of its own and is the small-appliance method: 'uses the appliance compressor or pressure; restricted to small appliances'. 'Uses the appliance compressor or pressure; permitted on large appliances' has the mechanism right but ignores the limit on where the method may be used. 'Uses the recovery-unit pump or compressor; restricted to small appliances' describes active equipment, which is not restricted in that way. 'Uses the recovery-unit pump or compressor; permitted on large appliances' is an accurate picture of active recovery, not of passive recovery.

Correct answer: Compliant: recovery satisfies the working-compressor minimum

With a working compressor the minimum is 90 percent, and exactly 90 percent meets a minimum: 'compliant: recovery satisfies the working-compressor minimum'. 'Noncompliant: recovery equals the working-compressor minimum' treats the minimum as a figure that must be beaten, when reaching it is enough. 'Noncompliant: household freezers require complete recovery' overstates the rule, since no small-appliance level asks for the whole charge. 'Compliant: household freezers carry the reduced minimum' reaches the right verdict from the wrong rule: the reduced 80 percent level is for a compressor that does not run, and this one works.

Correct answer: Factory-sealed design, 5-pound maximum charge

Type I is defined by construction and charge, and the two products share both: 'factory-sealed design, 5-pound maximum charge'. 'Home-appliance design, 5-pound maximum charge' swaps the factory seal for household use, which the definition does not mention. 'Factory-sealed design, shared refrigerant' is wrong because the refrigerant plays no part in the grouping, and a window unit and a refrigerator usually hold different refrigerants. 'Home-appliance design, shared refrigerant' names neither defining condition.

Correct answer: Active, self-contained recovery equipment with its own pump

With no working compressor and almost no pressure in the appliance, nothing inside the system can push the charge out, so the reliable choice is 'active, self-contained recovery equipment with its own pump'. 'Passive, system-dependent recovery equipment run off the appliance compressor' cannot work because that compressor does not run. 'Passive, system-dependent recovery equipment with a non-pressurized bag' depends on pressure in the appliance, and there is very little. 'Active, self-contained recovery equipment made for low-pressure chillers' is the wrong class of machine, built for Type III equipment.

Correct answer: PTAC: Section 608 Type I; car AC: Section 609

A sealed PTAC is a stationary, factory-sealed unit with a small charge, and a car system is a motor vehicle air conditioner: 'PTAC: Section 608 Type I; car AC: Section 609'. 'PTAC: Section 608 Type II; car AC: Section 609' gets the car right but treats the sealed PTAC as a field-charged high-pressure system. 'PTAC: Section 608 Type I; car AC: Section 608 Type II' gets the PTAC right but puts a vehicle system into a Section 608 type. 'PTAC: Section 609; car AC: Section 608 Type I' has the two programs reversed.

Correct answer: Impracticality of full active recovery of small sealed charges

Type I exists for a practical reason: 'impracticality of full active recovery of small sealed charges', so the EPA set recovery percentages and allowed passive methods for them. 'Negligible stratospheric ozone-layer impact of small sealed charges' is wrong because millions of small charges add up, which is why recovery is still required. 'De minimis status of small sealed charges' misuses a term that covers only the unavoidable traces lost during proper recovery. 'Private ownership of small sealed charges' is wrong because the rules bind whoever services or disposes of the appliance.

Correct answer: Charge exceeding the small-appliance limit

A factory seal is only half of the definition, and 8 pounds fails the other half, the 5-pound limit: 'charge exceeding the small-appliance limit'. 'Charge containing a high-pressure refrigerant' is wrong because the refrigerant plays no part in the definition. 'Commercial applications outside household use' and 'commercial building installation' are both wrong because Type I is not limited to household products; a commercial vending machine or water cooler with 5 pounds or less is a small appliance.

Correct answer: Working compressor = 90 percent; inoperative compressor = 80 percent

A running compressor helps drive the charge out, so the higher figure goes with it: 'working compressor = 90 percent; inoperative compressor = 80 percent'. 'Working compressor = 80 percent; inoperative compressor = 90 percent' has the two figures reversed. 'Working compressor = 90 percent; inoperative compressor = 90 percent' ignores the allowance for a compressor that cannot help. 'Working compressor = 80 percent; inoperative compressor = 70 percent' keeps the right order but sets both figures too low; 80 percent is the level for a compressor that cannot run, and no small-appliance level is 70 percent.

Correct answer: Active: built-in pump setup; passive method restricted to small appliances

Active means the recovery device does the pumping, and passive recovery is the small-appliance method: 'active: built-in pump setup; passive method restricted to small appliances'. 'Active: appliance-compressor setup; passive method restricted to small appliances' has the right limit but the wrong label, because drawing on the appliance compressor is what makes a method passive. 'Active: built-in pump setup; passive method permitted on large appliances' has the right label but the wrong limit. 'Active: appliance-compressor setup; passive method permitted on large appliances' is wrong on both points.

Correct answer: Field assembly and jobsite charging

A small appliance must leave the factory fully built, charged and hermetically sealed, and this unit did not: the reason is 'field assembly and jobsite charging'. 'High-pressure blended refrigerant charge' and 'chlorine-free refrigerant charge' both make the refrigerant the test, and the definition does not mention the refrigerant. 'Comfort cooling and heating applications' are not excluded as such: window air conditioners and packaged terminal heat pumps are small appliances too.

Correct answer: R-410A

R-410A is a high-pressure refrigerant, in the same Type II class as R-22 and R-404A. R-123 and R-113 are low-pressure refrigerants used in centrifugal chillers, which fall under Type III. R-1233zd is a newer low-pressure chiller refrigerant and is also Type III.

Correct answer: R-22, R-410A, R-404A

'R-22, R-410A, R-404A' is the only trio in which every member is a high-pressure refrigerant serviced under Type II. Each of the other trios hides one low-pressure refrigerant that belongs to Type III: 'R-134a, R-407C, R-11' and 'R-410A, R-407C, R-11' both include R-11, and 'R-22, R-134a, R-123' includes R-123.

Correct answer: Type II, high-pressure refrigerant

The answer is 'Type II, high-pressure refrigerant': R-404A is a high-pressure refrigerant, and high-pressure equipment such as a supermarket rack or a rooftop unit is Type II work. 'Type III, low-pressure refrigerant' gets the pressure class wrong; the low-pressure refrigerants are chiller refrigerants such as R-11 and R-123. 'Type I, low-pressure refrigerant' is wrong twice, on the pressure class and on the type. 'Type I, high-pressure refrigerant' has the pressure class right but the wrong type, since Type I covers only factory-sealed small appliances holding 5 pounds or less.

Correct answer: Gauges and recovery equipment with elevated pressure ratings

R-410A runs at roughly 50 to 70 percent higher pressure than R-22, so the practical consequence is 'gauges and recovery equipment with elevated pressure ratings'. 'Standard R-22 gauges and hoses with thorough purging' is wrong: purging does not raise a pressure rating. 'Storage and charging cylinders with reduced fill levels' is wrong for the same reason, since R-410A needs a recovery cylinder with a higher service pressure and the 80 percent fill limit applies to every recovery cylinder. 'Deeper evacuation and longer runtimes with standard machines' is wrong because both refrigerants sit in the same high-pressure class of the evacuation table, where the levels are 0 and 10 inches of mercury vacuum.

Correct answer: R-22

R-22 is the high-pressure HCFC that dominated residential and commercial air conditioning; its production and import ended on January 1, 2020. R-123 is also an HCFC, but it is a low-pressure chiller refrigerant. R-12 and R-11 are CFCs, not HCFCs, and their production ended in 1996; R-11 is also a low-pressure refrigerant.

Correct answer: Complete the leak repair, meeting the mandated deadline

Once the leak rate of an appliance this size passes the applicable threshold, the owner must 'complete the leak repair, meeting the mandated deadline', normally 30 days, with the repair then verified. 'Record the refrigerant additions, skipping the leak repair' confuses record keeping, which is required, with the repair it cannot replace. 'Postpone the leak repair, awaiting the seasonal shutdown' ignores the deadline, which runs for 30 days from the refrigerant addition that showed the excess leak rate. 'Notify the EPA regional office, delaying the leak repair' is not a step in the rule; the repair does not wait for a notice to the agency's regional office.

Correct answer: 50 pounds

The Section 608 leak-repair requirements apply to appliances with a full charge of 50 pounds or more. 5 pounds is the upper limit that defines a small appliance, 15 pounds is the charge above which system-dependent recovery equipment may not be used, and 200 pounds is the charge that changes the required evacuation level for high-pressure appliances.

Correct answer: Follow-up verification test proving repair success

The repair is proven by a 'follow-up verification test proving repair success', carried out after the initial verification test and once the system is back at normal operating conditions. 'Leak-rate calculation accompanying post-repair recharge' is a separate duty that measures later losses, not this repair. 'Quarterly leak inspection covering repair locations' describes the periodic inspections that follow an excess leak rate, not the verification of the repair. 'Written repair record listing refrigerant quantities' is record keeping, which the rule also requires, but a record documents the repair and does not verify that it worked.

Correct answer: Large fast-leaking charges producing the largest emissions

The rule targets big systems because of 'large fast-leaking charges producing the largest emissions': they emit the most, so requiring repair there limits emissions the most. 'Large high-pressure systems suffering the heaviest leakage' is wrong because operating pressure depends on the refrigerant, not on the size of the charge. 'Type I recovery covering the smaller systems' is wrong: Type I covers only factory-sealed appliances of 5 pounds or less, and many systems under 50 pounds are Type II. 'Small-system leaks eluding the standard leak detectors' is wrong because a leak detector works the same on a system of any size.

Correct answer: Excess leak rate: mandatory repair obligation

Topping off does not satisfy the rule, which says 'excess leak rate: mandatory repair obligation': a system holding 50 pounds or more that is over the leak rate must be repaired within the deadline, and this 60-pound comfort-cooling system is over it. 'Excess leak rate: mandatory single-recharge limit' invents a limit on additions; the rule looks at the leak rate, not at the number of top-offs. 'Excess leak rate: mandatory equipment shutdown' goes too far, because the system may keep running while the repair is made inside the deadline. 'Excess leak rate: mandatory appliance replacement' is also wrong, since retiring or retrofitting the appliance is only an alternative for an owner who chooses not to repair.

Correct answer: 10 inches of mercury vacuum

With recovery equipment made on or after November 15, 1993, a high-pressure appliance holding 200 pounds or more must be evacuated to 10 inches of mercury vacuum before it is opened for major service. 0 inches of mercury vacuum is the level for a high-pressure appliance holding less than 200 pounds. 4 inches of mercury vacuum is the level that applies when the recovery equipment was made before November 15, 1993. 15 inches of mercury vacuum is the level for the neighboring medium-pressure class at 200 pounds or more.

Correct answer: System evacuation level

The 200-pound line sets the 'system evacuation level', the recovery vacuum stated in inches of mercury: a high-pressure appliance holding 200 pounds or more must be pulled to a deeper vacuum than a smaller one. 'Leak-repair rule coverage' is decided by the 50-pound threshold. 'Small appliance rule coverage' is decided by the 5-pound limit on a factory-sealed charge. 'Recovery equipment type' turns on the 15-pound limit for system-dependent recovery equipment.

Correct answer: Inches of mercury vacuum

The Type II recovery levels are stated in inches of mercury vacuum, read on the vacuum side of a compound gauge. Millimeters of mercury absolute is the unit used for low-pressure Type III appliances, where the level is 25 mm Hg absolute. Pounds per square inch gauge and pounds per square inch absolute are pressure units; 0 psig is the level the rule sets for non-major repairs, and the levels for major service are given as a vacuum.

Correct answer: Heavier charge: deeper evacuation applies

The evacuation table splits high-pressure appliances at 200 pounds, so the answer is 'heavier charge: deeper evacuation applies': the 250-pound system must reach a deeper vacuum than the 150-pound system. 'Lighter charge: deeper evacuation applies' reverses the rule. 'Equal evacuation: shared high-pressure class' is wrong because the pressure class is only one of the two things the table looks at; within the high-pressure class the level still changes at 200 pounds. 'Equal evacuation: appliance sizes irrelevant' is wrong because the size of the charge is exactly what separates the two rows of the table.

Correct answer: Charge size and service type

For a high-pressure appliance the required level depends on 'charge size and service type': whether the charge is above or below 200 pounds, and whether the service is major or non-major. 'Charge size and compressor type' is wrong because the compressor does not set a Type II level; it is the Type I small-appliance rule that turns on whether the compressor runs. 'Refrigerant family and service type' is wrong because the table is organized by pressure class and charge, not by whether the refrigerant is a CFC, an HCFC or an HFC. 'Refrigerant family and compressor type' names two things that do not set the level.

Correct answer: 500 microns

The usual dehydration target is a deep vacuum of about 500 microns, low enough for moisture to boil off at room temperature. 750 microns, 1000 microns and 1500 microns are shallower readings passed on the way down, and none of them is the commonly taught target.

Correct answer: Moisture and noncondensable gas removal

A deep vacuum is pulled for 'moisture and noncondensable gas removal': at about 500 microns water boils off and air is drawn out. 'Refrigerant and compressor oil recovery' confuses dehydration with recovery, which is finished before the system is opened, and a vacuum pump does not remove the oil. 'Joint and valve leak detection' describes leak testing, which is done under pressure, not under a vacuum. 'Acid and sludge flushing' is wrong because acid and sludge are dealt with by filter-driers and an oil change, not by evacuation.

Correct answer: An electronic micron gauge

A deep vacuum of about 500 microns is confirmed with an electronic micron gauge, which reads absolute pressure in microns. An ordinary compound gauge on the manifold shows inches of mercury and cannot tell 500 microns from several thousand. A halide leak detector and a handheld leak detector both look for escaping refrigerant; neither measures how deep the vacuum is.

Correct answer: Leakage or lingering moisture

A reading that keeps climbing after the valves are closed points to 'leakage or lingering moisture': air is being drawn in through a leak, or water is still boiling off. 'Ongoing or deeper evacuation' cannot be right, because the pump is valved off and the reading is rising, not falling. 'Contaminated or saturated pump oil' is wrong because bad pump oil slows the pull-down while the pump runs; it does not make an isolated system rise. 'Reclaimed or recycled refrigerant purity' has nothing to do with a vacuum reading; purity to AHRI 700 is established by laboratory analysis of reclaimed refrigerant.

Correct answer: Leak-tight dry system with the noncondensable gas removed

A reading that stays at 500 microns with the pump isolated shows a 'leak-tight dry system with the noncondensable gas removed': the moisture is gone as well, so the system can be charged. 'Leak-tight wet system with the evaporator moisture frozen' is wrong because remaining moisture, frozen or not, keeps giving off vapor and the reading climbs. 'Isolated gauge with the appliance left unmeasured' is wrong because the standing test is read with the gauge on the system side of the isolation valve. 'Undersized pump with the vacuum left incomplete' is wrong because 500 microns is the target and the pump is not even connected during the test.

Correct answer: Nitrogen

Dry nitrogen is the recommended gas for pressure-testing a high-pressure system because it is inert and carries no moisture. Oxygen can explode on contact with compressor oil under pressure. Compressed air contains oxygen and moisture, so it brings the same hazard and wets the system. Pure refrigerant may not be used as a leak-test gas, because the test charge would be released; only a small trace of refrigerant mixed into nitrogen is allowed.

Correct answer: Explosive oil mixture once pressurized

Oxygen and compressed air are ruled out because of the 'explosive oil mixture once pressurized' they can form: under pressure they can ignite or explode on contact with the compressor oil that every system holds. 'Unreliable soap-bubble leak detection' is not the reason: a soap solution bubbles with any gas. 'Lingering noncondensable gas contamination' is not the reason, since nitrogen is also noncondensable and all of these gases are removed by evacuation. 'Refrigerant system corrosion damage' is not the reason either; a short pressure test does not corrode the system, and the hazard that rules these gases out is the explosion.

Correct answer: Detectable gas for electronic leak detection

Nitrogen cannot be sensed by a refrigerant leak detector, so a small trace of refrigerant is added; its role is 'detectable gas for electronic leak detection', giving the detector something to sense at the leak point. 'Pressure source for levels beyond nitrogen capacity' is wrong because the nitrogen supplies the pressure and the trace adds almost none. 'Fluorescent dye for ultraviolet lamp inspection' describes a different leak-finding method; a trace of refrigerant is not a dye and is not seen under a lamp. 'Drying agent for blocking moisture contamination' is wrong because it is the dry nitrogen that keeps moisture out; the trace plays no part in that.

Correct answer: Soap bubble solution brushed on suspect joints

'Soap bubble solution brushed on suspect joints' pinpoints a leak because escaping gas blows bubbles exactly where it comes out. 'Standing vacuum test read on micron gauges' and 'overnight standing pressure test on nitrogen' can each show that a leak exists somewhere, but neither shows where it is. 'Leak-rate calculation based on past usage logs' tells how much refrigerant the system loses in a year, not the location of the leak.

Correct answer: Dry nitrogen, optional refrigerant trace

The accepted procedure is 'dry nitrogen, optional refrigerant trace', followed by a check for leaks: nitrogen is inert and dry, and the trace lets an electronic detector respond. 'Filtered air, optional refrigerant trace' is wrong because air of any kind brings oxygen and moisture into the system. 'Pure oxygen, refrigerant trace omitted' is dangerous, since oxygen and compressor oil can explode under pressure. 'System refrigerant, trace gas omitted' is wrong because a full refrigerant charge may not be used as the test gas and would be lost through the leak.

Correct answer: The Montreal Protocol

HCFC-22 is an ozone-depleting substance, and its production and import were phased out under the Clean Air Act rules that carry out the Montreal Protocol. The Vienna Convention of 1985 is the framework treaty on the ozone layer and set no phase-out schedules. The Kigali Amendment of 2016 added the phasedown of HFCs, not HCFCs. The Paris Agreement deals with greenhouse gas emissions and climate, not ozone-depleting refrigerants.

Correct answer: Only from reclaimed, recycled, or recovered stock

Production and import of R-22 ended on January 1, 2020, so no newly made R-22 enters the market and the taught answer is 'only from reclaimed, recycled, or recovered stock'. Virgin R-22 produced before 2020 that is still in stock may also lawfully be used. 'Only from imported, permitted, or allocated stock' is wrong because no import allowances for R-22 are issued any longer. 'Only from licensed, labeled, or new stock' is wrong because no new R-22 may be produced, with or without a license. 'Only from purified, tested, or certified stock' is too narrow: that describes reclaimed refrigerant alone, while R-22 that is simply recovered or recycled may go back into equipment of the same owner.

Correct answer: The SNAP list of acceptable substitutes

EPA's Significant New Alternatives Policy program publishes the SNAP list of acceptable substitutes, which shows by end use whether a replacement refrigerant is acceptable and under what use conditions. 'The ASHRAE 34 table of acceptable uses' does not exist; ASHRAE Standard 34 assigns each refrigerant its designation and safety group. The AHRI 700 table of acceptable purity sets the contaminant limits that reclaimed refrigerant must meet, not which substitute may be used. 'The DOT list of acceptable refrigerants' does not exist either; DOT regulates how refrigerant cylinders are built and shipped.

Correct answer: Ozone-depleting HCFC chlorine content

The phase-out is about ozone, so the reason is the 'ozone-depleting HCFC chlorine content': R-22 contains chlorine and depletes ozone, while the chlorine-free HFCs have an ozone depletion potential of zero. 'Excessive HCFC global warming potential' is wrong because many HFCs have a higher global warming potential than R-22, which is why HFCs are now being phased down. 'Excessive HCFC flame propagation hazard' is wrong because R-22 is in the A1 safety group, lower toxicity and no flame propagation, and some HFCs, such as R-32, are mildly flammable. 'Elevated HCFC system pressure' is wrong because HFCs such as R-410A run at higher pressures than R-22.

Correct answer: Lubricant selection

The compatibility issue is 'lubricant selection': R-22 systems run on mineral oil, and many HFC substitutes need a different compressor oil, a synthetic such as POE, to return oil to the compressor. 'Contactor voltage' is wrong because the contactor switches the compressor on the same control voltage whatever the refrigerant. 'Blower speed' and 'thermostat setpoint' are wrong because neither part touches the refrigerant or depends on which one is in the circuit.

Correct answer: Lower toxicity, mild flammability

In the ASHRAE 34 safety groups the letter gives toxicity and the number gives flammability. A2L means 'lower toxicity, mild flammability': A is the lower toxicity class, and 2L is flammable with a low burning velocity. 'Higher toxicity, mild flammability' describes B2L, since B is the higher toxicity class. 'Lower toxicity, high flammability' describes A3, the group of hydrocarbons such as propane. 'Higher toxicity, high flammability' describes B3.

Correct answer: Ignition source control for flames and sparks

A2L means lower toxicity and mild flammability, so the precaution tied to the class is 'ignition source control for flames and sparks': open flames, sparks and other ignition sources are kept away from the work area. 'Toxic fume protection for lungs and skin' would fit a class B refrigerant; the A in A2L means lower toxicity. 'Extreme pressure ratings for hoses and gauges' is about pressure, which the safety group does not describe. 'Moisture precautions for water and steam' is wrong because the safety group rates only toxicity and flammability, not any reaction with water.

Correct answer: Refrigerant recovery to empty the system

An A2L refrigerant is mildly flammable, so the first step is 'refrigerant recovery to empty the system': the charge is recovered from the system before any heat is applied. 'Nitrogen purge to shield the refrigerant' is wrong because a nitrogen purge during brazing prevents oxide scale and is done on a system that has already been emptied. 'Nitrogen dilution to neutralize the charge' is wrong because the mixture could not be shown to be safe and the contaminated refrigerant would still have to be recovered. 'Wet rag wrap to cool the remaining charge' is wrong because a wet rag protects nearby components and does not keep a torch flame away from refrigerant.

Correct answer: Mild flammability, low burning velocity

The '2L' in A2L means 'mild flammability, low burning velocity': the refrigerant is in the lower flammability class and its flame spreads slowly. 'High flammability, fast burning velocity' describes class 3, the group of hydrocarbons such as propane. 'Reduced toxicity, generous exposure limit' is what the letter A says, not the 2L. 'Elevated toxicity, stricter exposure limit' is what the letter B would say.

Correct answer: Elevated system pressure

The design difference is the 'elevated system pressure' of R-410A, which operates roughly 50 to 70 percent above R-22, so compressors, coils, gauges and recovery equipment must be rated for it. 'Reduced system pressure' reverses the fact. 'Weaker fire hazard' and 'stronger toxicity hazard' are both wrong because the two refrigerants share the same A1 safety group: lower toxicity and no flame propagation.

Correct answer: The leak-repair rule at 50 pounds and high-pressure recovery procedures

R-404A is a high-pressure refrigerant and the rack holds well over 50 pounds, so the work is governed by 'the leak-repair rule at 50 pounds and high-pressure recovery procedures'. 'The Type I small-appliance limit and system-dependent recovery procedures' belongs to factory-sealed appliances of 5 pounds or less. 'The 25 mm Hg absolute vacuum and low-pressure recovery procedures' belongs to Type III chillers. 'The Section 609 certification and MVAC recovery procedures' applies to motor vehicle air conditioning, not to a supermarket system.

Correct answer: Shallower vacuum relative to larger charges

A high-pressure appliance holding less than 200 pounds needs a 'shallower vacuum relative to larger charges': 0 inches of mercury vacuum against 10 inches for a charge of 200 pounds or more, with recovery equipment made after November 15, 1993. 'Deeper vacuum relative to larger charges' reverses the table. 'Equal vacuum relative to low-pressure units' borrows the Type III level of 25 mm Hg absolute, which does not apply to high-pressure appliances. 'Equal vacuum relative to small appliances' borrows the Type I alternative level of 4 inches of mercury vacuum for small appliances.

Correct answer: Pull a deep vacuum near 500 microns to dehydrate the system

Moisture that entered while the system was open is removed when you 'pull a deep vacuum near 500 microns to dehydrate the system', because water boils off at that pressure. 'Pull a vacuum of 10 inches of mercury to dehydrate the system' uses a recovery level, which is far too shallow to boil water at room temperature. 'Pull a 25 mm Hg absolute vacuum to dehydrate the system' uses the Type III recovery level, about 25,000 microns, also far too shallow. 'Pull a vacuum for a full 30 minutes to dehydrate the system' is wrong because dehydration is judged by the micron reading, not by the clock.

Correct answer: High-pressure refrigerant class

A Type II appliance is identified by its 'high-pressure refrigerant class', with refrigerants such as R-22, R-404A or R-410A. 'Chiller noncondensable purge unit' and 'chiller rupture disc' are both features of a low-pressure Type III chiller, which runs below atmospheric pressure and draws air in through leaks. 'Small appliance refrigerant charge' points to the factory-sealed appliances of Type I, which hold 5 pounds or less.

Correct answer: Whether the leak-repair requirements cover the appliance

The 50-pound charge decides 'whether the leak-repair requirements cover the appliance': at 50 pounds or more, an excess leak rate triggers the repair deadlines. 'Whether the deep-vacuum requirements cover the appliance' is wrong because the deeper recovery vacuum is set by the 200-pound line. 'Whether the appliance is classed for passive recovery' depends on the 15-pound limit for system-dependent equipment. 'Whether the appliance is classed with small appliances' depends on the 5-pound limit for a factory-sealed charge.

Correct answer: Nitrogen, an inert gas nonexplosive in contact with oil

The right choice is 'nitrogen, an inert gas nonexplosive in contact with oil'. Dry nitrogen can be raised to test pressure safely, while the oxygen in compressed air can react violently with compressor oil under pressure. The option 'compressed air, with its oxygen taken out by evacuation' ignores that the hazard exists during the test itself, and air also loads the system with moisture. The option 'compressed air, dried sufficiently in a line filter' fails for the same reason: a filter does not take out the oxygen. The option 'nitrogen, a gas detected by electronic leak detectors' names the right gas for a wrong reason, since a detector responds to refrigerant, which is why a small trace of refrigerant is added to the nitrogen.

Correct answer: A deeper vacuum level

Major service calls for 'a deeper vacuum level'. When the repair is not major and the appliance will not be evacuated to the atmosphere when the work is finished, a high-pressure appliance only has to be brought to 0 psig; for a major repair on a system holding more than 200 pounds the table level applies, 10 inches of mercury vacuum with recovery equipment made after November 15, 1993. The answer 'an identical vacuum level' ignores that the level depends on the type of service, and 'a reduced vacuum level' reverses the rule. The answer 'an identical vacuum level held longer' confuses the recovery level with a standing vacuum test, which belongs to dehydration and leak checking.

Correct answer: Phaseout of production and import, leaving reclaimed supplies

The fact behind the scarcity is 'phaseout of production and import, leaving reclaimed supplies'. R-22 is an HCFC, and its phaseout under the Montreal Protocol and the Clean Air Act ended new manufacture and import on January 1, 2020, so service now depends on recovered and reclaimed refrigerant and on stock made before that date. The option 'phasedown of production and import, leaving yearly allowances' describes the allowance system of the HFC phasedown; R-22 has no new production at all. The option 'ban on reclaim and resale, leaving stockpiled supply' reverses the facts: reclaimed R-22 is exactly what may still be sold. The option 'ban on recovery and reuse, leaving imported stock' is wrong on both halves, since recovery is required and recovered R-22 may be reused, while imports have ended.

Correct answer: Mandatory recovery with flammable-rated equipment

The correct statement is 'mandatory recovery with flammable-rated equipment'. An A2L refrigerant is mildly flammable, but it is still covered by the recovery requirement, so the technician recovers it with a machine and cylinder designed for A2L service and keeps ignition sources away. The statement 'mandatory recovery with standard equipment' gets the duty right and the equipment wrong, because a standard machine may have switches and motors that can ignite the vapor. The statement 'voluntary recovery with flammable-rated equipment' gets the equipment right and the duty wrong, because mild flammability does not take a refrigerant out of the venting prohibition. The statement 'voluntary recovery with standard equipment' is wrong on both counts.

Correct answer: Repair and verification repeated until the leak rate is allowable

The next step is 'repair and verification repeated until the leak rate is allowable'. A failed follow-up verification test means the repair did not hold, so the leaks must be repaired and verified again before the appliance is in compliance. The option 'recharge and re-verification deferred until the annual inspection is due' leaves a known leak in service for months. The option 'documentation and close monitoring until the reduced charge is restored' is wrong because recordkeeping and monitoring do not replace the repair, and a short charge does not stop a leak. The option 'refrigerant recovery and system shutdown until the appliance is retired' is wrong because further repair attempts are allowed; retiring or retrofitting the appliance is a choice the owner may make, not a requirement after one failed test.

Correct answer: Recover, repair, evacuate to about 500 microns, then charge

The correct sequence is 'recover, repair, evacuate to about 500 microns, then charge'. The refrigerant is recovered first, the repair is made, and only then is the system pulled into a deep vacuum of roughly 500 microns, which boils off the moisture and removes air before the charge goes in. 'Recover, evacuate to about 500 microns, repair, then charge' puts the deep vacuum before the open repair, so the moisture that enters during the repair is never removed. 'Recover, repair, evacuate to about 0 psig, then charge' uses a recovery level, which is far too shallow to dehydrate a system, and 'recover, evacuate to about 0 psig, repair, then charge' makes both mistakes.

Correct answer: Gauges and hoses rated to the elevated pressure

The technician needs 'gauges and hoses rated to the elevated pressure'. R-410A runs at pressures roughly 50 to 70 percent higher than R-22, so every part of the gauge set, the hoses and the recovery equipment must be rated for it. The option 'hoses and fittings replaced on the existing gauges' is wrong because the gauges and manifold are part of the pressure rating too. The option 'existing gauges and a pressure-rated recovery cylinder' is wrong because a properly rated cylinder does nothing for an underrated gauge set. The option 'unchanged gauges and their built-in safety margin' is wrong because an R-22 gauge set has no such margin; R-410A equipment carries a much higher pressure rating.

Correct answer: Dry nitrogen with a small trace of refrigerant

The recommended mixture is 'dry nitrogen with a small trace of refrigerant'. The inert nitrogen raises the test pressure safely, and the trace of refrigerant gives an electronic leak detector something to sense at the leak. 'Compressed air with a small trace of refrigerant' is wrong because air brings oxygen and moisture into the system and can form an explosive mixture with oil under pressure. 'Dry nitrogen with the whole refrigerant charge' is wrong because the charge is recovered before the test and only a trace is used, so that little refrigerant is lost. 'Compressed air with the whole refrigerant charge' combines both errors.

Correct answer: Manifold gauge inaccuracy in a deep vacuum

The reason is 'manifold gauge inaccuracy in a deep vacuum'. The whole range from a rough vacuum down to 500 microns is a hair's width on the compound gauge of a manifold, so only an electronic micron gauge can confirm that dehydration is complete. The option 'missing vacuum scale on a manifold gauge' is wrong because the compound gauge does read below atmospheric pressure; it is simply too coarse. The option 'moisture level measurement by a micron gauge' is wrong because the instrument measures pressure, from which dryness is inferred. The option 'finer inches-of-mercury scale on a micron gauge' is wrong because a micron gauge reads in microns, a unit of absolute pressure, not in inches of mercury.

Correct answer: Noncompliant: at 50 pounds or more, an excessive leak rate requires repair

The accurate assessment is 'noncompliant: at 50 pounds or more, an excessive leak rate requires repair'. A 90-pound appliance is above the charge size at which the leak repair requirements apply, so once its leak rate exceeds the threshold the owner must have the leaks repaired within the deadline; adding refrigerant again and again is not a repair. The assessment 'compliant: at 50 pounds or more, recorded refrigerant additions replace repair' is wrong because records are required in addition to the repair, not in place of it. The assessment 'compliant: at 50 pounds or more, periodic leak inspections replace repair' is wrong for the same reason: leak inspections come on top of the repair and do not stand in for it. The assessment 'noncompliant: at 50 pounds or more, repair requires an immediate system shutdown' reaches the right verdict for a reason the rule does not contain: the appliance may keep running while the repair is made on time.

Correct answer: R-410A is a high-pressure refrigerant

The correct pairing is 'R-410A is a high-pressure refrigerant', which places it in the equipment a Type II technician services. 'R-11 is a high-pressure refrigerant' and 'R-113 is a high-pressure refrigerant' are wrong because both are low-pressure CFCs used in older centrifugal chillers, and 'R-245fa is a high-pressure refrigerant' is wrong because it is a low-pressure HFC used in some newer chillers. All three belong to Type III.

Correct answer: Inertness, ruling out combustion and explosive mixtures

The reason is 'inertness, ruling out combustion and explosive mixtures'. Oxygen under pressure can react explosively with compressor oil, while nitrogen does not support combustion at all, which makes it safe both for purging during brazing and for pressurizing a system for a leak test. The option 'dryness, absorbing moisture and acid from exposed piping' is wrong because nitrogen does not absorb acid, and moisture is removed by evacuation. The option 'coolness, chilling the joint and sparing the valve seals' is wrong because the slow purge flow is there to keep oxygen away from the hot copper, not to cool it. The option 'stability, tripping a detector and pinpointing leaks' is wrong because a leak detector responds to refrigerant, not to nitrogen.

Correct answer: HCFC phaseout of production and import

The development is the 'HCFC phaseout of production and import'. R-22 is an HCFC, and since January 1, 2020 no new R-22 has been made or imported, so an older unit is serviced with recovered, recycled or reclaimed refrigerant or with stock made before that date. The option 'HFC phasedown of production and import' names the wrong program, since the phasedown applies to HFCs such as R-410A. The option 'HCFC phaseout of sale and use' names the right program and the wrong effect: R-22 already in stock may still be sold and used. The option 'HFC phasedown of sale and use' is wrong on both counts.

Correct answer: Prevention of blend fractionation

A zeotropic blend is charged as a liquid for the 'prevention of blend fractionation'. The components boil at different temperatures, so vapor drawn from the cylinder is richer in the more volatile ones; liquid leaves the cylinder in the designed proportions. The answer 'prevention of temperature glide' is wrong because glide is a property of the blend that no charging method removes. The answer 'prevention of moisture absorption' is wrong because moisture is taken up by the oil when a system stands open, which the charging method does not control. The answer 'prevention of flash gas' describes vapor forming in the liquid line of a running system, not a charging concern.

Correct answer: 200-pound charge threshold and service type

The two facts are the '200-pound charge threshold and service type'. A repair that is not major may need only 0 psig, while a major repair uses the table level, and for high-pressure appliances that level changes at a charge of 200 pounds; the date the recovery equipment was made also affects the exact figure. In '200-pound charge threshold and annual leak rate' the leak rate is a fact that decides leak repair, not evacuation. In '200-pound charge threshold and compressor condition' the condition of the compressor is what decides the 90 or 80 percent recovery rule for small appliances. In '200-pound charge threshold and room temperature' the room temperature does not appear in the evacuation table at all.

Correct answer: Oxygen displacement together with mild flammability

The combined hazard is 'oxygen displacement together with mild flammability'. In the A2L safety group the letter A means lower toxicity and 2L means lower flammability with a slow burning velocity, so the risks in an enclosed room are a leak pushing out the breathable air and the vapor reaching an ignition source; ventilation and control of ignition sources address both. The hazard 'elevated toxicity together with mild flammability' would describe group B2L, and 'elevated toxicity together with high flammability' would describe a class B refrigerant with class 3 flammability. The hazard 'oxygen displacement together with high flammability' would describe group A3, such as propane.

Correct answer: R-22: chlorinated HCFC under phaseout; R-410A: chlorine-free high-pressure HFC blend

The accurate statement is 'R-22: chlorinated HCFC under phaseout; R-410A: chlorine-free high-pressure HFC blend'. R-22 depletes ozone because of its chlorine, and R-410A, a blend of the HFCs R-32 and R-125, has an ozone depletion potential of zero and runs at higher pressures than R-22. The statement 'R-22: chlorinated HCFC under phaseout; R-410A: chlorine-free high-pressure HFO blend' gets R-22 right and R-410A wrong, since R-410A is a blend of two HFCs, not of HFOs. The statement 'R-22: chlorinated CFC under phaseout; R-410A: chlorine-free high-pressure HFC blend' gets R-410A right and R-22 wrong, since R-22 still carries hydrogen and is an HCFC. The statement 'R-22: chlorinated CFC under phaseout; R-410A: chlorine-free high-pressure HFO blend' is wrong about both.

Correct answer: Pressure below atmospheric at room temperature, vacuum operation

The defining trait is 'pressure below atmospheric at room temperature, vacuum operation'. A low-pressure refrigerant such as R-11 or R-123 boils at about room temperature under one atmosphere, so in a chiller the evaporator side sits below atmospheric pressure. The description 'boiling point far below room temperature, pressurized operation' fits a high-pressure refrigerant such as R-22, and 'boiling point far below room temperature, vacuum operation' joins that high-pressure trait to a result it cannot produce. The description 'pressure below atmospheric at room temperature, pressurized operation' starts correctly and ends backward: a machine whose refrigerant is below atmospheric pressure at room temperature does not stay pressurized.

Correct answer: A subatmospheric pressure

At room temperature the saturation pressure of a low-pressure refrigerant is 'a subatmospheric pressure', one below atmospheric pressure, which is why the low side of the chiller runs in a vacuum and why leaks draw air inward. The answer 'a strong positive pressure' describes high-pressure refrigerants such as R-22 and R-410A. The answer 'a 15 psig positive pressure' is the setting of the rupture disc on the shell, not the pressure of the refrigerant at room temperature. The answer 'a standard atmospheric pressure' is wrong because that is the condition at the boiling point, which for these refrigerants lies near or above room temperature.

Correct answer: A Type III low-pressure appliance

The chiller is 'a Type III low-pressure appliance', because a low side that sits in a vacuum at room temperature is the mark of a low-pressure refrigerant. 'A Type II high-pressure appliance' would hold a refrigerant such as R-22 or R-410A, which stays well above atmospheric pressure at room temperature, and 'a Type II low-pressure appliance' joins the wrong type number to the right pressure class, since low-pressure equipment is Type III. 'A Type I high-pressure appliance' is wrong because Type I covers factory-sealed small appliances holding 5 pounds or less, not a large building chiller.

Correct answer: R-11 and R-123

The low-pressure pair is 'R-11 and R-123', the CFC used in older centrifugal chillers and the HCFC that replaced it. 'R-12 and R-500' lists two medium-pressure refrigerants. 'R-11 and R-500' and 'R-12 and R-123' each join one low-pressure refrigerant to a medium-pressure one, since R-12 and R-500 are both medium-pressure CFC refrigerants serviced under Type II.

Correct answer: R-11

The traditional low-pressure refrigerant of older centrifugal chillers is R-11, a CFC whose production ended with the CFC phaseout. R-12 is a CFC and R-502 is a blend that contains one, but neither is a low-pressure refrigerant. R-123 is a low-pressure refrigerant, but it is the HCFC that replaced R-11, not a CFC.

Correct answer: R-123

The HCFC that replaced R-11 in centrifugal chillers is R-123, a low-pressure refrigerant with a far lower ozone depletion potential. R-22 is an HCFC, but it is a high-pressure refrigerant. R-113 and R-114 were both used in centrifugal chillers, but they are CFCs like R-11 itself, not HCFCs.

Correct answer: R-1233zd

The modern low-pressure choice used in place of R-123 is R-1233zd, an HFO with a near-zero ozone depletion potential and a very low global warming potential. R-245fa is a low-pressure refrigerant, but it is an HFC with a high global warming potential. R-1234ze and R-1234yf are low-GWP HFOs, but neither is a low-pressure refrigerant: R-1234ze is used in place of R-134a in medium-pressure chillers, and R-1234yf mainly in motor vehicle air conditioning.

Correct answer: Type III, since R-123 is a low-pressure refrigerant

The answer is 'Type III, since R-123 is a low-pressure refrigerant'. Certification type follows the pressure class of the refrigerant, and R-123, like R-11 and R-1233zd, is low pressure. 'Type II, since R-123 is a high-pressure refrigerant' misclassifies R-123. 'Type II, since the chiller exceeds 200 pounds' and 'Type III, since the chiller exceeds 200 pounds' both rest on charge size, which sets evacuation levels within a type but does not decide between Type II and Type III.

Correct answer: Air and moisture leaking into the chiller shell

The concern is 'air and moisture leaking into the chiller shell'. Where the machine is below atmospheric pressure, the outside air is at the higher pressure, so a leak carries air and its moisture inward. 'Refrigerant and oil leaking out of the piping' is the leak behavior of a high-pressure system. 'Air and moisture leaking out of the condenser' has the direction wrong, since air that gets in stays trapped in the condenser until the purge unit removes it. 'Refrigerant and oil leaking into the water loop' is wrong because at a tube leak the water is usually at the higher pressure and enters the refrigerant side.

Correct answer: Subatmospheric pressure on the low side

The reason is 'subatmospheric pressure on the low side'. Flow through a leak always runs from the higher pressure to the lower, and in a low-pressure chiller the higher pressure is outside. The option 'purge unit suction on the condenser shell' is wrong because the purge unit removes air that has already entered; it does not create the vacuum. The option 'heavy refrigerant vapor in the condenser shell' is wrong because density does not move gas through a leak, pressure difference does. The option 'nonvolatile refrigerant in the evaporator' is wrong because these refrigerants evaporate readily; air enters because of the pressure difference.

Correct answer: It raises the condensing pressure and reduces efficiency

The effect of trapped air is 'it raises the condensing pressure and reduces efficiency'. Noncondensables collect in the condenser, where they take up heat-transfer surface and add their own pressure to that of the refrigerant, so the compressor works against a higher head. 'It lowers the condensing pressure and reduces efficiency' has the direction reversed. 'It raises the suction pressure and reduces efficiency' and 'it lowers the suction pressure and reduces efficiency' put the effect on the wrong side of the machine, since the air is carried to the condenser and stays there.

Correct answer: Noncondensable air has leaked into the vessel and accumulated

The likely cause is 'noncondensable air has leaked into the vessel and accumulated'. A low-pressure chiller draws air in through any leak, and that air gathers in the condenser, raising the condensing pressure and cutting efficiency even with a full charge. 'Moisture has entered the chiller and frozen the expansion valve' would restrict flow and starve the evaporator rather than raise the condensing pressure. 'Compressor oil has migrated to the evaporator and coated the tube bundle' would hurt heat transfer in the evaporator and lower its pressure, not raise the head. 'The purge unit has run too long and removed refrigerant' would show up as a falling charge, which the technician has ruled out.

Correct answer: Air and noncondensable removal with the refrigerant retained

The purpose of a purge unit is 'air and noncondensable removal with the refrigerant retained'. Air that leaks into the machine collects at the top of the condenser; the purge unit draws off that gas, condenses the refrigerant mixed with it, returns the refrigerant, and discharges the air. The option 'moisture and acid removal from the entire charge in circulation' describes the work of a filter-drier. The option 'refrigerant and oil removal to a separate storage vessel' describes a pump-out or recovery unit. The option 'air and moisture removal by a prolonged deep evacuation' describes the vacuum pump used for dehydration after the machine has been opened.

Correct answer: An air leak admitting noncondensables

Excessive purging most likely means 'an air leak admitting noncondensables'. The purge unit runs when air builds up in the condenser, so a sharp rise in purge run time points to air being drawn into the machine faster than before. The conditions 'excess charge flooding the condenser tubes' and 'fouled tubes raising the condensing pressure' can both raise the head pressure, but neither puts more air in the condenser for the purge unit to remove. The condition 'a failed rupture disc releasing refrigerant' would show as a loss of charge, not as extra purging.

Correct answer: Expel refrigerant vapor with the purged air

Without good separation a purge unit would 'expel refrigerant vapor with the purged air'. The gas it draws from the condenser is a mixture of air and refrigerant vapor, and whatever refrigerant is not condensed and returned leaves with the air; high-efficiency units cut that loss to a very small amount. The option 'draw moist outside air into the refrigerant' is wrong because the discharge flows outward. The option 'return separated gases to the refrigerant' is wrong because expelling the air is the whole job of the unit. The option 'draw lubricating oil from the refrigerant' is wrong because a purge unit handles gas from the top of the condenser, not oil.

Correct answer: Reduced refrigerant loss in the purged air

High-efficiency purge units are preferred for their 'reduced refrigerant loss in the purged air': they give up far less refrigerant for each pound of air they expel. Better separation of refrigerant from the noncondensables sharply cuts the emissions that older purge units produced. The option 'positive shell pressure blocking inward leaks' is wrong because a purge unit removes air after it has leaked in and does not change the operating pressure. The option 'moisture removal replacing post-service evacuation' is wrong because a system opened for service must still be evacuated. The option 'shutdown operation with a vapor-free condenser' is wrong because the condenser always holds refrigerant vapor and purge units work while the chiller runs.

Correct answer: 25 mm Hg absolute

With recovery equipment made on or after November 15, 1993, a low-pressure appliance is evacuated to 25 mm Hg absolute. The figure of 25 inches of mercury vacuum confuses the units: the low-pressure level is 25 mm Hg absolute, a much deeper vacuum. The level of 10 inches of mercury vacuum belongs to high-pressure appliances, and 10 psig is the highest pressure allowed when a low-pressure system is leak tested, not a recovery level.

Correct answer: Absolute pressure, measured up from a perfect vacuum

The figure is 'absolute pressure, measured up from a perfect vacuum': 25 mm Hg absolute means only 25 millimeters of mercury remain above a total vacuum. 'Gauge pressure, measured down from atmospheric pressure' describes inches of mercury vacuum, the scale used for high-pressure recovery levels. 'Absolute pressure, measured down from atmospheric pressure' and 'gauge pressure, measured up from a perfect vacuum' each join one scale to the reference point of the other, since absolute pressure starts at a perfect vacuum and gauge pressure starts at atmospheric pressure.

Correct answer: 25 mm Hg absolute

A low-pressure chiller opened for major service must be recovered to 25 mm Hg absolute. The figure of 25 inches of mercury vacuum confuses the units: 25 mm Hg absolute is a much deeper vacuum. The level of 15 inches of mercury vacuum is the medium-pressure figure for a charge of 200 pounds or more from the same table, and 15 psig is the setting of the rupture disc on a low-pressure vessel, not a recovery level.

Correct answer: 25 mm Hg absolute, a separate low-pressure standard

The reason is '25 mm Hg absolute, a separate low-pressure standard'. Because these machines already run below atmospheric pressure, the rule sets an absolute-pressure target for them that is separate from the inches-of-mercury levels used for high-pressure equipment. The option '25 inches Hg vacuum, a deeper Type II recovery standard' is wrong because that figure is not a Type II level; it is the classic mix-up of inches of mercury vacuum with millimeters of mercury absolute, which is a far deeper vacuum. The option '0 psig, the small-charge recovery standard' is wrong because that level belongs to small high-pressure charges, and 0 psig would leave most of the vapor in a low-pressure machine. The option '500 microns, the deep-vacuum dehydration standard' confuses recovery with dehydration.

Correct answer: 15 psig

The rupture disc on a low-pressure chiller is typically set to relieve at 15 psig, because the shell is built for pressures near or below atmospheric. The figure of 10 psig is the highest pressure that should be used to leak test a low-pressure system, chosen to stay safely under the disc setting. Settings of 25 psig and 30 psig are above what the shell of a low-pressure chiller is protected for.

Correct answer: Relief of excess pressure to protect the shell

The rupture disc is there for the 'relief of excess pressure to protect the shell'. If the pressure in the vessel climbs to the disc setting of about 15 psig, the disc bursts and releases the pressure so that the shell itself does not fail. The option 'removal of air to limit the condenser pressure' describes the purge unit. The option 'compressor cutout at high condenser pressure' describes a high-pressure cutout, a control that acts before a relief device is needed. The option 'slight positive shell pressure at idle' describes a heating method used to keep air from leaking into an idle machine.

Correct answer: Noncombustible mix with the system oil

Dry nitrogen is the leak-test gas because it forms a "noncombustible mix with the system oil": oxygen or compressed air under pressure can react violently with oil, and nitrogen does not react at all. "Tracer gas response at the detector" is wrong because an electronic detector senses refrigerant, and nitrogen only supplies the pressure. "Condensable vapor inside the shell" is wrong because nitrogen is itself a noncondensable that has to be removed afterward. "Low pressure inside the nitrogen tanks" is wrong because a nitrogen cylinder holds very high pressure and needs a regulator to keep the test at or below 10 psig.

Correct answer: Rupture disc failure near 15 psig

A low-pressure chiller is protected by a rupture disc that bursts at roughly 15 psig, so raising it to 30 psig means "rupture disc failure near 15 psig" and the loss of the charge. "Rupture disc failure near 10 psig" gives the wrong figure for the disc: 10 psig is the most a low-pressure system should be raised to for a leak test. For the same reason "nitrogen test limit near 15 psig" is wrong, since 15 psig is the disc setting and the test limit is 10 psig, and "nitrogen test limit near 25 psig" is wrong because 25 belongs to the recovery level of 25 mm Hg absolute, which is a vacuum and not a test pressure.

Correct answer: R-123

R-123 has the lower ozone depletion potential (ODP). It is an HCFC, and the hydrogen in its molecule lets most of it break down before it reaches the stratosphere, which is one reason it replaced R-11 in low-pressure chillers. R-11 is a CFC and is the reference refrigerant for the scale, with an ODP of 1. "Equal ODP values" is wrong because the two differ by a wide margin, and "zero ODP values" is wrong because the two refrigerants contain chlorine and deplete ozone.

Correct answer: Closer attention to room ventilation and to exposure level readings

The letter in a safety classification gives toxicity and the number gives flammability, so B1 means higher toxicity with no flame propagation. R-123 therefore calls for "closer attention to room ventilation and to exposure level readings", because its allowable exposure is lower than that of R-11. "Closer attention to ignition sources and to flammable vapor levels" reads the classification the wrong way round: the 1 marks R-123 as nonflammable. "Closer attention to internal pressure and to rupture disc condition" is ordinary practice on a low-pressure chiller and has no connection to the toxicity class. "Closer attention to frostbite protection and to liquid skin contact" fits high-pressure refrigerants that flash cold; R-123 boils near room temperature.

Correct answer: R-123: reduced ODP, elevated toxicity

Measured against R-11, the accurate comparison is "R-123: reduced ODP, elevated toxicity": R-123 is an HCFC with a small fraction of the ozone depletion potential of the CFC R-11, yet it is classified B1 while R-11 is A1. "R-123: elevated ODP, reduced toxicity" reverses the two facts. "R-123: elevated ODP, elevated toxicity" has the toxicity right and the ozone effect wrong, and "R-123: reduced ODP, reduced toxicity" has the ozone effect right and the toxicity wrong.

Correct answer: Low-side vacuum at room temperature

Low-pressure refrigerants such as R-11 and R-123 boil near room temperature, so the sign of a Type III appliance is a "low-side vacuum at room temperature". "Positive gauge pressure at shutdown" describes a high-pressure appliance, which stays well above atmospheric pressure even when idle. "Condenser at several hundred psig" also describes high-pressure equipment such as an R-410A system. A "factory-sealed unit at five pounds" fits the definition of a small appliance, which is Type I and is set by charge size, not by operating pressure.

Correct answer: Routine vacuum operating pressures

A low-pressure appliance is already below atmospheric pressure in normal operation, so a vacuum on the gauge says little about how empty it is. The reason for the absolute figure is its "routine vacuum operating pressures": 25 mm Hg absolute states how close to a perfect vacuum the system must be pulled. "Unusually large refrigerant charges" is wrong because the size of the charge does not decide the unit; high-pressure systems of 200 pounds and up are still rated in inches of mercury. "High-efficiency purge emission limits" is wrong because the purge unit removes air while the chiller runs and plays no part in the recovery level. "Rupture disc burst settings" is wrong because the disc guards against overpressure near 15 psig, which is unrelated to how deep the recovery vacuum is.

Correct answer: Recovery, then certified reclamation or disposal

R-11 is a CFC that is no longer made, so every pound has to be captured: "recovery, then certified reclamation or disposal". An EPA-certified reclaimer returns it to the purity of new product so it can serve other R-11 chillers, and refrigerant that cannot be reclaimed goes to a proper disposal facility. "On-site recycling, then resale or donation" is wrong because refrigerant that changes owners must first be reclaimed by an EPA-certified reclaimer. "Recovery, then mixing with spare HCFC or HFC stock" is wrong because mixed refrigerants often cannot be reclaimed at all. "On-site recycling, then disposable cylinder storage or shipment" is wrong because a disposable cylinder is never refilled; recovered refrigerant goes into approved refillable containers.

Correct answer: Refrigerant carried out with the air

A purge unit removes the air that leaks into a low-pressure chiller, but the concern is "refrigerant carried out with the air", so the refrigerant lost with each pound of air is limited and high-efficiency purge units are used. "Compressor oil carried out with the air" is wrong because the regulated substance in the discharge is the refrigerant, not oil. "System pressure lowered by the purged air" is wrong because lowering the head pressure is the purpose of purging and is no reason to limit what the discharge contains. "Ozone layer damaged by the purged air" is wrong because air does no harm to the ozone layer; the refrigerant mixed with it does.

Correct answer: Ongoing leak drawing air into the chiller

A purge unit removes air but does not stop it from entering, so air that keeps coming back points to an "ongoing leak drawing air into the chiller", whose low side is below atmospheric pressure; the leak has to be found and repaired. "Dissolved air freed from the refrigerant" is wrong because refrigerant does not carry a store of air that it keeps giving off. "Sump heater driving air from the oil" is wrong because warm oil gives up dissolved refrigerant, and it is not a continuing source of air. "Excess charge forcing air into the vessel" is wrong because extra refrigerant raises the liquid level and brings in no air.

Correct answer: Low-pressure system in a vacuum, high-pressure system pressurized

At room temperature a low-pressure refrigerant such as R-123 has a saturation pressure under one atmosphere, while a high-pressure refrigerant such as R-22 or R-410A sits far over it. So the answer is "low-pressure system in a vacuum, high-pressure system pressurized", which is why air leaks into one and refrigerant leaks out of the other. "Low-pressure system pressurized, high-pressure system in a vacuum" has the two reversed. "Low-pressure system pressurized, high-pressure system pressurized" is right about the high-pressure system alone, and "low-pressure system in a vacuum, high-pressure system in a vacuum" is right about the low-pressure system alone.

Correct answer: Air leakage or refrigerant leaving the oil

A system that has been recovered fully and is tight holds its vacuum, so a rising pressure means recovery is not finished: the cause is "air leakage or refrigerant leaving the oil", where dissolved refrigerant is still boiling out. The technician waits, recovers again and, if the pressure keeps climbing toward atmospheric, looks for a leak. "Tube icing or refrigerant condensing" is wrong because condensing refrigerant would make the pressure fall, not rise. "A tight shell or a full refrigerant recovery" is wrong because a tight, empty shell stays at the level it was pulled to. "A running purge unit or a refrigerant return" is wrong because the purge unit serves a running chiller and plays no part once the charge has been recovered.

Correct answer: CFC phaseout, with a reduced-ODP low-pressure replacement

Production of CFCs ended in 1996, and R-11 has the highest ozone depletion potential (ODP) of the common chiller refrigerants. The explanation is "CFC phaseout, with a reduced-ODP low-pressure replacement": R-123 is an HCFC with a small fraction of the ODP of R-11, and it let the chiller keep its low-pressure design. "CFC phaseout, with a zero-ODP low-pressure replacement" is right about the pressure and wrong about the ozone effect, since R-123 still has a small ODP. "CFC phaseout, with a reduced-ODP high-pressure replacement" is wrong because R-123 is a low-pressure refrigerant. "CFC phaseout, with a zero-ODP high-pressure replacement" makes the two mistakes together.

Correct answer: Vacuum operation, a purge unit, R-11 or R-123

Type III covers low-pressure appliances, which are recognized by "vacuum operation, a purge unit, R-11 or R-123": the evaporator runs below atmospheric pressure, air leaks in, and a purge unit removes it. "High-pressure operation, a liquid receiver, R-22 or R-410A" describes Type II equipment. "Cascade operation, a low-temperature stage, R-13 or R-503" describes very high-pressure equipment, which also falls under Type II. "Sealed-system operation, a process stub, R-134a or R-600a" describes a small appliance, which is Type I.

Correct answer: Nearly pure noncondensables in the discharge

A purge unit condenses the refrigerant out of the gas it draws from the condenser and sends that refrigerant back to the chiller. A high-efficiency unit does this so well that the result is "nearly pure noncondensables in the discharge" and very little refrigerant. "Noncondensable gas returned to the condenser" is wrong because air sent back to the condenser would defeat the purpose of purging. "Fixed refrigerant share in the discharge" is wrong because the aim is to keep refrigerant loss as close to zero as the unit can manage. "Noncondensable gas stored in purge drums" is wrong because the purge drum separates the two; the air leaves and the refrigerant goes back.

Correct answer: Noncondensable buildup and corrosion

An open low-pressure chiller fills with air and takes on moisture, and the result is "noncondensable buildup and corrosion" that reduce performance: air collects in the condenser and raises head pressure, and moisture forms acids and rust inside the shells. "Low head pressure and compressor oil foaming" has the effect backward, because air raises head pressure. "Metering device ice and liquid floodback" describes a low-temperature system; a chiller evaporator runs above freezing. "Deeper vacuum and compressor oil losses" is wrong because air adds its own pressure to the system and makes the vacuum shallower.

Correct answer: R-11

R-11 is the CFC among the low-pressure refrigerants. A CFC carries chlorine and no hydrogen, so nearly all of it survives to reach the stratosphere, and R-11 is the reference for the scale with an ozone depletion potential of 1. R-123 is an HCFC with a small fraction of that value. R-245fa is an HFC with no chlorine and an ozone depletion potential of zero. R-1233zd is a newer low-pressure refrigerant whose ozone depletion potential is close to zero.

Correct answer: Burst near 15 psig, protecting the shell

A rupture disc is a one-time device: the expected action is "burst near 15 psig, protecting the shell", and the disc must then be replaced. "Burst near 10 psig, protecting the shell" has the action right and the figure wrong; 10 psig is the most a low-pressure system should be raised to for a leak test, which keeps the test safely under the disc setting. "Lift near 15 psig, reseating afterward" describes a spring-loaded relief valve, which closes again when the pressure falls, and "lift near 10 psig, reseating afterward" makes the two mistakes together.

Correct answer: Refrigerant loss needing a high-efficiency purge unit

A purge unit is meant to release air and keep the refrigerant, so refrigerant that can be noticed in the discharge means "refrigerant loss needing a high-efficiency purge unit", a purge unit that separates the two far more completely and meets emission limits. "Normal purge unit operation discharging the trapped air" is wrong because a unit that works well releases almost none of the charge. "Chiller overcharge relieved by the purge unit" is wrong because a purge unit removes noncondensables and is not a way to correct the charge. "Leak-free chiller shell with a stopped purge unit" is wrong because a tight machine gives the purge unit little to do, so it runs seldom and discharges very little.

Correct answer: Inward air leaks, found by nitrogen pressurization

On a high-pressure system refrigerant escapes at a leak and can be detected while the unit runs. On a low-pressure chiller the opposite happens: "inward air leaks, found by nitrogen pressurization", with the pressure kept at or below 10 psig. "Inward air leaks, found by shop-air pressurization" has the leak direction right and the gas wrong: compressed air carries oxygen and moisture, and oxygen under pressure can react violently with the oil, so an inert gas such as dry nitrogen is used. "Outward vapor leaks, found by detector scanning" describes the high-pressure system, where a detector finds escaping refrigerant in operation. "Outward vapor leaks, found by deep evacuation" is wrong on the direction and on the method, since a deep vacuum draws in extra air and does not show where the leak is.

Correct answer: 25 mm Hg absolute

Low-pressure appliances recovered with equipment made on or after November 15, 1993 must be evacuated to 25 mm Hg absolute. 25 inches of mercury vacuum confuses the units: it is a much shallower vacuum, and the current table lists 25 mm Hg absolute for low-pressure appliances whatever the age of the recovery equipment. 15 inches of mercury vacuum is the level for medium-pressure appliances holding 200 pounds or more and does not apply to a low-pressure chiller. 15 psig is a positive pressure, the approximate setting of the rupture disc, and not a recovery level.

Correct answer: Chiller unit in a vacuum, drawing outside air inward

Air enters a machine where the pressure inside is lower than the pressure outside. That is the case in a low-pressure chiller: "chiller unit in a vacuum, drawing outside air inward", and the purge unit removes that air from the top of the condenser. "Chiller unit at positive pressure, trapping air" is wrong because a machine at positive pressure pushes refrigerant out at a leak and takes in no air. "Rooftop unit in a vacuum, drawing outside air inward" is wrong because a rooftop unit stays above atmospheric pressure, which is the very reason it has no purge unit. "Rooftop unit at positive pressure, trapping air" has the pressure right but is wrong about the air, since nothing is drawn in for a purge unit to remove.

Correct answer: Room ventilation and refrigerant monitoring

In a safety classification the letter B means higher toxicity and the number 1 means no flame propagation. Because of that higher toxicity, an enclosed room with an R-123 chiller needs "room ventilation and refrigerant monitoring", so a leak is sensed and cleared before exposure limits are passed. "Explosion-proof motors and flammable-gas alarms" answers a flammability hazard, and R-123 is in flammability class 1. "Sealed room and refrigerant containment" is wrong because sealing the room traps the vapor where people work. "System relief and pressure alarms" answers a pressure hazard; R-123 is a low-pressure refrigerant and the toxicity class says nothing about pressure.

Correct answer: Low-side vacuum drawing air inward

Gas moves through an opening from the higher pressure to the lower one. In a running low-pressure chiller the explanation is the "low-side vacuum drawing air inward", so very little refrigerant gets out. "Purge unit suction at the leak point" is wrong because a purge unit removes air that has entered and does not capture refrigerant at a leak. "Low vapor loss from a liquid charge" is wrong because the direction of flow is set by the pressure difference, not by how much of the charge is liquid. "Heavy vapor settling inside the shell" is wrong because a heavy vapor escapes readily whenever the pressure inside is the higher one.

Correct answer: A very low ozone depletion potential and a low global warming potential

R-1233zd is a low-pressure refrigerant chosen for new centrifugal chillers because it offers "a very low ozone depletion potential and a low global warming potential", an improvement on R-123 on both counts. "A very low ozone depletion potential and a high global warming potential" is the profile of an older HFC; the global warming potential of R-1233zd is close to 1. "A very high ozone depletion potential and a low global warming potential" is wrong because its ozone depletion potential is close to zero and well below that of R-123. "A very high ozone depletion potential and a high global warming potential" is the profile of a CFC such as R-11.

Correct answer: New disc at an identical set pressure

A rupture disc is a one-time device: once it has burst it cannot close again. The technician must fit a "new disc at an identical set pressure", which on a low-pressure chiller is about 15 psig. "New disc at an increased set pressure" is wrong because the shell would then be allowed to exceed the pressure it was designed to be protected at. "Reseated disc with a vacuum test" and "reseated disc with a bubble test" are wrong because a burst disc is torn metal that cannot be reseated, whatever leak test follows; a spring-loaded relief valve is the device that reseats.

Correct answer: Low-pressure appliance: 25 mm Hg absolute

R-123 is a low-pressure refrigerant, so the chiller is Type III: "low-pressure appliance: 25 mm Hg absolute". "Low-pressure appliance: 25 inches of mercury vacuum" has the right category and the wrong level: it confuses the units, since the current table lists 25 mm Hg absolute for low-pressure appliances whatever the age of the recovery equipment, and 25 inches of mercury vacuum is far shallower. "High-pressure appliance: 4 inches of mercury vacuum" and "high-pressure appliance: 0 psig" put the chiller in the wrong category; 4 inches of mercury and 0 psig are levels from the high-pressure rows of the table.

Correct answer: Its vacuum keeps drawing in air that must be removed, while the high-pressure system leaks outward

A purge unit is needed wherever air can get in during operation. For the chiller, "its vacuum keeps drawing in air that must be removed, while the high-pressure system leaks outward" and so does not collect air while it runs. "Its refrigerant keeps giving off air that must be removed, while the high-pressure system stays sealed" is wrong because the noncondensables in a chiller are air from outside, not a product of the refrigerant. "Its oil keeps collecting moisture that must be removed, while the high-pressure system uses a filter-drier" is wrong because a purge unit is fitted to remove air, and moisture arrives with that air. "Its large charge keeps collecting acid that must be removed, while the high-pressure system holds too little" is wrong because the size of the charge does not decide whether air enters.

Correct answer: Reduced ozone harm, elevated toxicity, tighter exposure controls

R-123 is an HCFC with a much smaller ozone depletion potential than the CFC R-11, but it is classified B1 where R-11 is A1. The tradeoff is "reduced ozone harm, elevated toxicity, tighter exposure controls": added ventilation and refrigerant monitoring. "Elevated ozone harm, reduced toxicity, relaxed exposure controls" reverses the two facts. "Reduced ozone harm, elevated flammability, tighter fire codes" mistakes the toxicity class for flammability; the 1 in B1 and in A1 means that the two refrigerants show no flame propagation. "Elevated ozone harm, reduced flammability, relaxed fire codes" is wrong about the ozone layer and about flammability.

Correct answer: Teardown once recovery reaches 25 mm Hg absolute

The charge is recovered to the required level, and only afterward is a low-pressure chiller opened: "teardown once recovery reaches 25 mm Hg absolute". "Teardown once recovery reaches 25 inches of mercury vacuum" confuses the units and uses a far shallower vacuum that leaves much more refrigerant behind; the current table lists 25 mm Hg absolute for low-pressure appliances whatever the age of the recovery equipment. "Teardown once recovery reaches 500 microns of vacuum" uses the deep-vacuum figure for dehydration ahead of charging, not the recovery requirement. "Teardown once recovery reaches 0 psig" uses a level from the high-pressure rows of the table; a low-pressure chiller at 0 psig still holds a large amount of refrigerant vapor.

Correct answer: Inward leakage of atmospheric air; nitrogen test limit of 10 psig

A low-pressure chiller runs in a vacuum and does not push refrigerant out at a leak, so there is nothing to detect until the pressure is raised with nitrogen: "inward leakage of atmospheric air; nitrogen test limit of 10 psig". "Inward leakage of atmospheric air; nitrogen test limit of 15 psig" gives the right behavior and the wrong limit; 15 psig is roughly where the rupture disc bursts, so the test pressure stays at or below 10 psig. "Outward leakage of refrigerant; nitrogen test limit of 10 psig" describes the behavior of a high-pressure unit, and "outward leakage of refrigerant; nitrogen test limit of 15 psig" has the behavior and the limit wrong.

Correct answer: High ozone depletion potential and room ventilation

R-11 is a CFC, and its vapor is heavier than air and can displace the oxygen in a tight room. The two concerns are its "high ozone depletion potential and room ventilation": the charge has to be recovered and never released, and the space has to be ventilated for the safety of the technician. "High operating pressure and relief protection" is wrong because R-11 is a low-pressure refrigerant. "Low ozone depletion potential and toxicity controls" is closer to the profile of R-123, the B1 replacement; R-11 has the highest ozone depletion potential of the chiller refrigerants. "Mild flammability and frostbite protection" is wrong because R-11 is classified A1 and boils near room temperature.