Return-side smoke detection is required on multi-story systems with capacity of

Return-side smoke detection is required on multi-story systems with capacity of

• A. 5000 CFM
• B. 15000 CFM
• C. 2000 CFM
• D. 10000 CFM

Answer: (B)

Focusing on where smoke will be detected in a ventilation system helps ensure early warning and quick isolation on multi-story buildings. When the system moves a large amount of air, smoke can be drawn into the return ductwork and travel between floors. Placing smoke detectors on the return side catches smoke in that path before it spreads, enabling faster alarm activation and control. The requirement applies when the system’s capacity reaches 15,000 CFM or more, so a multi-story system at or above this flow rate must include return-side smoke detection. Capacities well below that threshold do not automatically trigger this requirement, although detectors may still be used for other reasons.

Focusing on where smoke will be detected in a ventilation system helps ensure early warning and quick isolation on multi-story buildings. When the system moves a large amount of air, smoke can be drawn into the return ductwork and travel between floors. Placing smoke detectors on the return side catches smoke in that path before it spreads, enabling faster alarm activation and control. The requirement applies when the system’s capacity reaches 15,000 CFM or more, so a multi-story system at or above this flow rate must include return-side smoke detection. Capacities well below that threshold do not automatically trigger this requirement, although detectors may still be used for other reasons.