Why does an R-123 equipment room need a refrigerant sensor and not just an oxygen-deprivation sensor?

Safety · EPA 608 Type III. The correct answer, and the reasoning behind it.

ASHRAE Standard 15 equipment-room requirements and refrigerant sensors.

The question

Why does an R-123 equipment room need a refrigerant sensor and not just an oxygen-deprivation sensor?

• AR-123 is flammable in normal room air
• BR-123 is lighter than air and rises out of reach of the oxygen sensor
• COxygen sensors do not work in chiller rooms
• DR-123 can harm people at levels far too low to cut oxygenCorrect answer

Why “R-123 can harm people at levels far too low to cut oxygen” is correct

An oxygen sensor alarms only after leaked refrigerant has pushed oxygen down to about 19.5 percent, which takes several percent refrigerant in the air. R-123 is in the higher-toxicity group under ASHRAE Standard 34, with an exposure limit of 50 ppm, so a refrigerant detector is needed to warn far earlier. Current Standard 15 requires that kind of detector for every refrigerant.

Source: EPA: Test Topics; ASHRAE 15-2016 Addendum c (detector set point at OEL); ASHRAE Standard 34

Why the other answers are wrong

• R-123 is flammable in normal room air — R-123 is classed as non-flammable; the concern is toxicity.
• R-123 is lighter than air and rises out of reach of the oxygen sensor — R-123 vapor is heavier than air and collects in low places.
• Oxygen sensors do not work in chiller rooms — Oxygen sensors work; they just respond too late for a toxic refrigerant.

Practice more of this

More EPA 608 Type III practice questions, or see every EPA 608 practice test.