What is the primary function of duct smoke detectors in HVAC systems?

• A. To detect smoke in air streams before it reaches occupied spaces
• B. To measure humidity levels
• C. To detect gas leaks in rooms
• D. To monitor CO levels in parking spaces

Answer: (A)

Duct smoke detectors are designed to catch smoke in the air flow of a building’s HVAC system before it reaches occupied spaces. Placed in supply and return ducts, they detect smoke early so the fire-control system can respond by shutting down air handlers, closing dampers, and alerting occupants. This helps prevent smoke from circulating through the building, aiding safe evacuation and limiting smoke spread. They aren’t meant to measure humidity, detect gas leaks, or monitor CO levels in parking areas, which involve different sensors and safety goals.