In a return air duct supplying an air handler rated 2000 CFM or greater, which safety device is required?

• A. Smoke detector
• B. Fire damper
• C. CO detector
• D. Heat sensor

Answer: (A)

In large return air ducts feeding an air handler (2000 CFM or greater), a smoke detector is required to automatically shut down the air handler if smoke is detected. This helps prevent circulating smoke through the building and gives a rapid response to a potential fire, working with the building’s fire alarm system.

Fire dampers are used where ducts pass through fire-rated barriers to slow fire spread, not for sensing smoke or controlling the air handler. CO detectors monitor carbon monoxide in spaces, not the duct-based smoke conditions that would necessitate shutting down the equipment. Heat sensors may detect high temperatures but aren’t the standard device mandated for early smoke detection in large return ducts.