Which gas does EPA's test outline list as the best choice for pressurizing a high-pressure system for a leak test?
Leak detection · EPA 608 Type II. The correct answer, and the reasoning behind it.
Signs of leaks in high-pressure systems and leak testing before charging.
The question
Which gas does EPA's test outline list as the best choice for pressurizing a high-pressure system for a leak test?
- Pure R-22
- Compressed air
- Oxygen
- Nitrogen aloneCorrect answer
Why “Nitrogen alone” is correct
Nitrogen alone is listed as the preferred leak test gas. It is inert, dry, inexpensive, and exempt from the venting prohibition, so releasing it after the test harms nothing.
Source: EPA: Test Topics; 40 CFR 82.154(a)
Why the other answers are wrong
- Pure R-22 — Pure refrigerant is the least preferred choice because it is lost when the test gas is released.
- Compressed air — Compressed air brings in moisture and can form an explosive mix with oil under pressure.
- Oxygen — Oxygen can explode in contact with compressor oil and must never be used.
Practice more of this
More EPA 608 Type II practice questions, or see every EPA 608 practice test.
Unofficial, not affiliated with the EPA or any EPA-approved certifying organization. Questions are original practice written from public EPA material, not real exam questions.