A large quantity of refrigerant has leaked into a basement equipment room where no ventilation has been running. What is the hazard facing the first person who opens that door?
- AThe refrigerant will have turned to an acid mist while it pooled, and that mist burns exposed skin on contact
Acid forms when refrigerant decomposes at high temperature, over a torch flame or a hot surface. Refrigerant pooling in a cool basement has nothing to break it down, so no acid mist is waiting at the door.
- The vapor is heavier than air and settles low in the room, displacing the oxygen a person needs to breathe
- CThe vapor will ignite from any spark thrown by the electrical equipment running in the room
The common refrigerants in this equipment are not readily ignited under these conditions, and framing the hazard as fire sends the responder looking for ignition sources while the danger is the air itself.
- DThe vapor raises the pressure inside the closed room enough to cause ear injury on the way in
A leak does not pressurize a room in any measurable way. The room stays at atmospheric pressure with the wrong gas filling the lower part of it, so nothing about entering threatens the ears.
Why B is correct
These vapors are denser than air and accumulate at the lowest point in a space. Because they simply take the place of air, the danger is a lack of oxygen rather than any toxic effect, and it develops without a strong odor or any other warning to the person entering.
What this question is testing
This item checks understanding of vapor density and the asphyxiation mechanism, and whether the candidate can pick the real hazard out of a list of plausible-sounding alternatives.
On the job
Machinery rooms and basements are built with vapor sensors and exhaust fans for exactly this reason, and those systems are worth checking before entering rather than after. The same hazard shows up in walk-in freezers with a leaking evaporator and in elevator pits under a leaking line. The habit is to open the space up, run ventilation, and wait, and to have a second person outside the room who knows you went in.
Memory technique
Refrigerant sinks. It fills the basement from the floor up and takes the air with it.
Exam tip
The refrigerant inhalation hazard on this exam is oxygen displacement in a low or enclosed space. Ventilate first, enter second.
Where to look it up
Refrigerant vapors are heavier than air and accumulate in low areas, displacing oxygen. Ventilation is required before entry.