Duct detectors are usually required on systems with a capacity over how many cubic feet per minute?

Duct detectors are usually required on systems with a capacity over how many cubic feet per minute?

• A. 1000 cfm
• B. 2000 cfm
• C. 3000 cfm
• D. 4000 cfm

Answer: (B)

Duct detectors are used to monitor smoke in the building’s air distribution paths. When smoke is detected in the ducts, the fire alarm system can alert occupants and, if needed, shut down or control the air handling units to prevent spreading smoke through the building. The threshold is set for larger HVAC systems because these systems move a lot of air, which can distribute smoke quickly. For most codes and practices, that threshold is when the system capacity exceeds about 2,000 cubic feet per minute. So systems over 2,000 cfm usually require duct detectors to provide early warning and better smoke control.

Duct detectors are used to monitor smoke in the building’s air distribution paths. When smoke is detected in the ducts, the fire alarm system can alert occupants and, if needed, shut down or control the air handling units to prevent spreading smoke through the building.

The threshold is set for larger HVAC systems because these systems move a lot of air, which can distribute smoke quickly. For most codes and practices, that threshold is when the system capacity exceeds about 2,000 cubic feet per minute. So systems over 2,000 cfm usually require duct detectors to provide early warning and better smoke control.