If a multi-story HVAC system has a capacity of 10000 CFM, is return-side smoke detection required under NFPA 90A?

• A. Yes
• B. No
• C. Only if the building has more than four stories
• D. Depends on occupancy type

Answer: (B)

In NFPA 90A, return-side smoke detectors are not required for every air-handling system. The standard places the requirement based on the system’s size and the potential for smoke to spread through the return path as part of a smoke-control strategy. A 10,000 CFM system is considered small-to-moderate in capacity, so it does not meet the threshold that would mandate return-side detection in this context. Therefore, return-side smoke detection is not required for this scenario. The decision isn’t driven by the number of stories or occupancy type here; those factors aren’t the determining criteria in this case.