CSLB C-20 HVAC ContractorControls, Electrical and SafetyEasy
A homeowner installs a carbon monoxide detector in a hallway near bedrooms. Per general safety guidelines, where should CO detectors be mounted for proper sensing?
- AOn the ceiling only, since CO is lighter than air
- BAt any height on a wall or ceiling, away from vents and dead air corners
- COnly inside the garage where vehicles are parked
- DDirectly inside the furnace closet, at floor level
Show answer & explanationAnswer & explanation
Correct answer: B. At any height on a wall or ceiling, away from vents and dead air corners
CO mixes evenly with air rather than sharply stratifying, so detectors can be mounted at any height as long as they are kept away from dead-air corners, supply vents, and areas with excessive humidity, per manufacturer and safety code guidance.
Why the other options are wrong
- A. CO is nearly the same density as air, so ceiling-only placement is not required.
- C. Garages need their own detectors, but relying only on garage placement leaves living spaces unprotected.
- D. Placing it directly in the furnace closet floor risks nuisance alarms and is not the recommended general location.
CO Detector Placement
Carbon monoxide detectors should be installed near sleeping areas, away from vents and dead-air pockets, since CO mixes with air rather than settling at floor or ceiling level.
- CO density ~ same as air (slightly lighter)
- Avoid corners, humid areas (bathrooms), and near supply registers
- Install near each sleeping area per most jurisdictions
Memory trick: CO mixes like fog—spread evenly, avoid dead air corners.