Detectors installed in an air duct system are substitutes for room smoke detectors.

• A. True
• B. False
• C. Sometimes
• D. Not specified

Answer: (B)

Duct detectors and room smoke detectors serve different purposes, so one cannot replace the other. Detectors in air ducts monitor smoke particles in the HVAC air stream and are mainly used to protect the ductwork and control mechanical systems (like shutting down fans or triggering a building-wide alarm to limit smoke spread). They do not provide life-safety coverage in each occupied space, and smoke in a room may not reach the duct quickly enough to give timely warning. For proper life-safety detection, room smoke detectors are required in designated areas, and duct detectors are typically used as supplementary devices rather than substitutes.