Are smoke detectors permitted to be located in air streams?

Are smoke detectors permitted to be located in air streams?

• A. No
• B. Yes
• C. Only in ducts
• D. Only with AHJ approval

Answer: (A)

The main idea is that smoke detectors are meant to sense smoke in the space being protected, not in the moving air. Placing a detector directly in an air stream exposes it to high-velocity airflow, dilution, and turbulence, which can carry smoke past the sensor or cause false alarms and sensor contamination. Standard detectors installed in rooms or ceilings rely on smoke settling into the sensing chamber. If you need to monitor air flow, that’s typically done with a duct-mounted detector, which is a specialized device with its own installation rules. So for a typical smoke detector used to protect a space, locating it in an air stream is not permitted.

The main idea is that smoke detectors are meant to sense smoke in the space being protected, not in the moving air. Placing a detector directly in an air stream exposes it to high-velocity airflow, dilution, and turbulence, which can carry smoke past the sensor or cause false alarms and sensor contamination. Standard detectors installed in rooms or ceilings rely on smoke settling into the sensing chamber. If you need to monitor air flow, that’s typically done with a duct-mounted detector, which is a specialized device with its own installation rules. So for a typical smoke detector used to protect a space, locating it in an air stream is not permitted.