Leak detection and repair on the EPA 608

Answer: D. do not contain chlorine

• AWrong: these blends are not low-pressure refrigerants, and pressure doesn't decide whether a detector senses them.
• BWrong: flash point doesn't affect what an electronic detector can sense.
• CWrong: acoustic detectors are an option, but the reason a CFC detector fails is the chemistry of the blend.
• DCorrect: many older electronic detectors sense chlorine, so chlorine-free HFC blends need a detector made for them.

Many retrofit and drop-in substitutes are HFC or HFO blends. Because they contain no chlorine, older CFC-calibrated electronic leak detectors can't sense them.

Answer: B. The system must be retrofitted or retired within 12 months.

• AWrong: the deadline is 12 months, and the rule speaks of retrofit or retirement, not just replacement.
• BCorrect: if the owner won't repair, a retrofit or retirement plan is due within 30 days and must be completed within one year.
• CWrong: six months is too short; the plan must be carried out within 12 months.
• DWrong: 12 months is right, but the options are retrofit or retirement, not only replacement.

If the owner decides not to repair, a retrofit or retirement plan is due within 30 days, and the retrofit or retirement must be completed within one year (40 CFR 82.157, eCFR as of October 5, 2026). These deadlines apply to appliances with 50 lb or more of an ozone-depleting refrigerant.

Answer: C. Isolate unit and recover refrigerant.

• AWrong: temporary sealing and pulling a vacuum don't meet the definition; the refrigerant must be evacuated from the isolated system.
• BWrong: venting the charge is prohibited; mothballing requires recovery.
• CCorrect: mothballing means taking the system out of service and evacuating its refrigerant to at least atmospheric pressure.
• DWrong: a nitrogen flush doesn't remove the refrigerant properly and would release it.

Mothballing means evacuating the refrigerant from the appliance, or its isolated section, to at least atmospheric pressure and shutting it down. That pauses the leak-repair deadlines until the system is recharged.

Answer: D. Initial before charging, follow-up after operation.

• AWrong: the initial test is done when the repair is complete, not during evacuation.
• BWrong: nitrogen can be part of a test, but the timing is what the rule sets: before recharging, then after reaching normal operation.
• CWrong: when the system was evacuated, the initial test comes before recharging, and the follow-up is due within 10 days, not 30.
• DCorrect: if the system was evacuated, run the initial verification test before recharging and the follow-up once it reaches normal operating conditions.

Technicians must verify repair effectiveness. The initial verification test is performed before adding refrigerant, while the follow-up test occurs after the appliance returns to its normal operating characteristics.

Answer: A. No, recovery is required

• ACorrect: mothballing requires evacuating the refrigerant to at least atmospheric pressure; a shut-down system still fully charged doesn't qualify.
• BWrong: securing the power doesn't make it mothballed; the charge has to be removed.
• CWrong: mothballing is available to commercial and comfort cooling appliances too, not only industrial process refrigeration.
• DWrong: being offline isn't enough; a mothballed system must have its refrigerant evacuated.

Shutting an appliance down doesn't pause the repair clock. Mothballing means evacuating the refrigerant to at least atmospheric pressure and then shutting the appliance down (40 CFR 82.152, eCFR as of October 5, 2026).

Answer: C. Close receiver king valve, recover the low-side refrigerant, and then introduce dry nitrogen.

• AWrong: pressurizing the whole system before isolating it tests both sides at once and mixes trace gas and nitrogen into the charge.
• BWrong: pumping down without isolating and recovering the low side doesn't confine the test to the low side.
• CCorrect: closing the king valve isolates the low side; recovering its refrigerant before adding dry nitrogen lets you pressure-test it alone.
• DWrong: pressurizing a running system with nitrogen adds non-condensables to the charge and doesn't isolate the leak.

Isolate the low side by closing the king valve. Recover the remaining low-side refrigerant, then add dry nitrogen to pressure-test without pushing contaminants into the high side.

Answer: A. Pressurizing the system with a few ounces of system refrigerant and an inert gas.

• ACorrect: a few ounces of the system's own refrigerant raised to test pressure with nitrogen lets a detector find leaks without wasting the charge.
• BWrong: compressed air brings in moisture and, mixed with oil and refrigerant under pressure, can be dangerous.
• CWrong: using refrigerant alone wastes refrigerant and mixes a different refrigerant into the system.
• DWrong: releasing the charge to look for leaks is illegal venting.

For safety and effectiveness, a chill water system should be pressurized with an inert gas such as nitrogen and a few ounces of system refrigerant. This method avoids the risks associated with using flammable or improper gases.

Answer: B. Pressurized with an inert gas and leak checked

• AWrong: compressed air adds moisture and can be explosive with oil under pressure; use nitrogen.
• BCorrect: a new system is leak-tested with an inert gas such as dry nitrogen before it is evacuated and charged.
• CWrong: charging before leak-testing risks losing refrigerant through leaks you haven't found yet.
• DWrong: waiting 24 hours doesn't check for leaks.

After installation, pressurize the system with nitrogen or another inert gas and leak-check it before anything else. Electronic or ultrasonic leak detectors are typically used to locate leaks.

Answer: C. Pressurize to manufacturer's specified test pressure with nitrogen and trace refrigerant

• AWrong: using refrigerant alone for pressure testing wastes refrigerant and releases it at every leak.
• BWrong: compressed air adds moisture and oxygen to the system and must not be used.
• CCorrect: nitrogen to the manufacturer's test pressure with a trace of refrigerant lets an electronic detector find leaks safely.
• DWrong: 'maximum system pressure' is not a test pressure; use the manufacturer's specified pressure with a regulator and relief valve.

When leak testing an R-410A system, pressurize with nitrogen to the manufacturer's specified test pressure, not exceeding the system design pressure. Add a trace amount of refrigerant and use an electronic leak detector to locate any leaks.

Answer: C. 30 days.

• AWrong: the repair deadline is 30 days, not 45.
• BWrong: 90 days is wrong; 120 days applies only when an industrial process shutdown is needed.
• CCorrect: leaks in an appliance over its leak-rate threshold must be repaired within 30 days.
• DWrong: the standard repair deadline is 30 days, not 60.

For refrigeration systems with 50 or more pounds of a regulated refrigerant that exceed the threshold leak rate, repairs must be completed within 30 days to bring leakage below the maximum rate.

Answer: D. Repair the leaks or develop a retrofit/retirement plan within 30 days

• AWrong: topping off without repair doesn't meet the rule once the leak rate is exceeded.
• BWrong: an immediate shutdown isn't required; the rule allows 30 days to repair or plan a retrofit.
• CWrong: topping off without fixing the leak doesn't satisfy the rule; the owner still has to repair within 30 days or start a retrofit or retirement plan.
• DCorrect: for appliances with 50 lb or more of ODS refrigerant, leaks must be repaired within 30 days, or a retrofit/retirement plan made.

When a high-pressure system exceeds its allowable annual leak rate, the owner must repair the leaks or develop a retrofit/retirement plan within 30 days and implement it within one year.

Answer: D. Visual inspection for oil spots or stains

• AWrong: replacing parts before finding the leak wastes time and money.
• BWrong: adding refrigerant first hides the problem and keeps the leak going.
• CWrong: 500 psi could exceed the system's test pressure; follow the manufacturer's rating.
• DCorrect: oil traces at joints show where refrigerant has been escaping, so look first.

The first step when troubleshooting a potential refrigerant leak is a visual inspection to check for oil spots or stains, as these often indicate refrigerant leaks because oil travels with refrigerant.

Answer: A. Ultrasonic leak detector

• ACorrect: an ultrasonic detector picks up the hiss of escaping gas and works on high-pressure split systems.
• BWrong: a visual check finds clues like oil stains but can't confirm small leaks by itself.
• CWrong: submerging a split system in water isn't practical; dunk tests are for small parts.
• DWrong: checking the charge tells you refrigerant is missing, not where it leaks.

An ultrasonic leak detector is an acceptable leak detection method for high-pressure systems because it can detect the high-frequency sound produced by refrigerant escaping through a small opening, without being affected by wind or other environmental factors.

Answer: C. Repair the leak before adding additional refrigerant

• AWrong: adding refrigerant without fixing the leak lets it keep escaping.
• BWrong: venting the rest of the charge is illegal.
• CCorrect: find and repair the leak first so the new charge isn't lost.
• DWrong: switching refrigerants doesn't fix the leak.

Repairing before adding refrigerant is good practice: a new charge would leak out too. EPA's leak-repair deadlines apply only to appliances with 50 lb or more of an ozone-depleting refrigerant.

Answer: B. Because nitrogen is inert and minimizes any chemical reaction risks

• AWrong: availability isn't the main reason; nitrogen is chosen because it's inert and dry.
• BCorrect: dry nitrogen is inert and won't react with oil or refrigerant, unlike oxygen or air.
• CWrong: nitrogen is used for leak testing, not for speeding up liquid recovery.
• DWrong: nitrogen isn't detected because it rises; leaks are found with bubbles, pressure drop, or a trace gas.

Nitrogen is inert, non-flammable, and does not react with refrigerants, ensuring safe and accurate leak detection.

Answer: C. Introduce a trace amount of compatible refrigerant and pressurize with dry nitrogen

• AWrong: oxygen under pressure can explode in contact with oil.
• BWrong: compressed air adds moisture and oxygen to the system and is unsafe under pressure with oil.
• CCorrect: dry nitrogen with a trace of compatible refrigerant pressurizes the system safely and lets an electronic detector find leaks.
• DWrong: drawing in air contaminates the system and doesn't pressurize it for a leak test.

The safest leak testing method for high-pressure systems involves adding a trace amount of compatible refrigerant, then pressurizing with dry nitrogen to use an electronic leak detector.