A large charge has leaked out of a chiller into a closed mechanical room with the door shut and no ventilation running. What is the primary hazard facing anyone who walks in?
- AFrostbite from vapor contacting exposed skin
Direct contact with liquid refrigerant can cause frostbite, and that is a real hazard when charging, but the room-scale danger from a large vapor release is oxygen displacement.
- BFire, because refrigerant vapor ignites readily at room temperature
Common refrigerants of this type are not readily flammable at room temperature, which is why the hazard is asphyxiation rather than fire.
- Asphyxiation, because the vapor displaces oxygen in the room
- DElectric shock from static charge built up by the escaping vapor
Static discharge is not the recognized hazard associated with a large refrigerant release in a confined space. Escaping vapor does not build a charge capable of shocking someone entering the room.
Why C is correct
Common refrigerants are heavier than air and are not toxic in the ordinary sense, so the danger is simple displacement. The vapor pushes oxygen out of the low parts of the room, and someone entering breathes an atmosphere that cannot support them. Loss of consciousness can occur before the person recognizes anything is wrong.
What this question is testing
The item tests the primary confined-space hazard of a refrigerant release and your ability to rank it above other real but secondary hazards such as frostbite. Recognizing that the vapor is heavier than air is the underlying concept. Confined and low spaces are the setting the exam uses for this hazard.
On the job
Machinery rooms are built with ventilation and refrigerant monitors precisely because of this hazard, and the first thing to check when you get a call like this is whether that ventilation is actually running. Techs have died going down into basements and pits after a leak. The discipline that saves people is boring: ventilate first, do not enter alone, and treat a strong refrigerant smell in a closed low space as a reason to stay outside and open it up.
Memory technique
40 CFR Part 82, Subpart F
Exam tip
Refrigerant vapor is heavier than air, settles low, and displaces oxygen. Asphyxiation is the confined-space hazard.
Where to look it up
Heavy vapor sinks, oxygen goes, and so do you. Ventilate before you enter.