A technician performs triple evacuation on a Type II system. What gas is used to break the vacuum between evacuations?
a.Compressed shop air
b.Oxygen
c.Dry nitrogen
d.Carbon dioxide from a fire extinguisher
Explanation
Dry nitrogen is used to break the vacuum between evacuations because it is inert, moisture-free, and helps sweep out remaining moisture. Oxygen is dangerous because it can react explosively with refrigeration oil, and shop air adds moisture. Triple evacuation with nitrogen dilutes and removes noncondensables and water vapor more effectively than a single pull-down.
This topic, taught in full in the EPA Section 608 Certification guide. EPA 608 Universal Study Guide (2026) — Core + Type I/II/III, with the 2027 A2L update — PDF + EPUB, $14.99 · 14-day refund →
Practice all 240 questions free — no signup required.
Own the complete EPA Section 608 Certification guide — PDF + EPUB, $14.99 →
Related questions on this topic
- A technician wants to speed up vapor recovery from an R-410A condensing unit. Which practice will increase recovery speed?
- After replacing a compressor on an R-410A system, a technician needs to remove moisture and noncondensables before charging. Which procedure is the correct way to dehydrate the system?
- During evacuation of a Type II system, a technician wants to confirm the system has reached a deep, dry vacuum. Which instrument gives the precise reading needed?
- A technician is charging an R-410A system that uses a near-azeotropic blend. To keep the blend's composition correct, how should refrigerant be removed from the cylinder during charging?
- A technician checks the charge on an R-22 system that uses a fixed orifice (piston) metering device. Which measurement is the primary method to verify the charge?
- A technician is checking the charge on a system equipped with a thermostatic expansion valve (TXV). Which measurement is the preferred way to verify the charge on a TXV system?
Last reviewed: · editorial process
PrepPass team · Verified against EPA Section 608 Technician Certification Exam · How we review