How should the emergency exhaust for a chiller machine room be arranged?
- ADrawing air from the ceiling and returning it to the building air handler
Ceiling level suction misses the dense vapor layer near the floor, and returning the air to the building spreads the hazard into occupied spaces.
- BRecirculating room air through a carbon filter and back into the space
Carbon filters are not a control for refrigerant vapor, and recirculating the air keeps the refrigerant inside the building. The vapor would keep circulating through the space that the workers are trying to clear.
- Taking suction near the floor and discharging outside the building
- DBlowing outside air across the chiller with a portable fan on the floor
A portable fan stirs the room without removing anything and can push vapor toward doorways and workers instead of exhausting it.
Why C is correct
Taking suction low captures the heaviest concentration of vapor, and discharging outdoors removes it from the building rather than relocating the hazard. This arrangement is what actually clears a machine room after a release and makes it safe to re-enter after monitoring confirms the space is clean.
What this question is testing
This tests the ventilation half of machine room safety and connects it to the vapor behavior the candidate is expected to already understand. It measures whether you can connect vapor density to system design, and whether you recognize that recirculating air relocates a hazard instead of removing it.
On the job
Before you begin work that could release refrigerant, find the emergency exhaust switch and confirm the fan actually runs. Plenty of machine rooms have an exhaust system that was disconnected during a remodel or whose damper is painted shut. Also look at where the discharge lands outside, because a discharge next to a fresh air intake or a loading dock moves the problem instead of solving it, and that is worth reporting to the building owner.
Memory technique
Low in, outside out. Never send it back into the building.
Exam tip
Ventilation answers should always pull from low and discharge outside. Recirculation is never correct for refrigerant.
Where to look it up
Emergency machine room ventilation takes suction near the floor, where heavy refrigerant vapor collects, and discharges outdoors.