Interpretation #9571
Published August 14, 2026
Original Request
- Code Version
- 2023
- Code
- MECHANIC
- Code Description
- Chapter
- 6
- Section
- 606.2.2
- Topic
- Common supply
Question
If two individual air handlers that do not share duct work with the two additional units in the same mechanical room have a combined air flow of all air handlers added together is above 2,000 cfm with no dividing walls, do the units require duct detectors?
Answer Published 08/11/2026 at 3:49 PM
Possibly, If the units have a common return air inlet from the space exceeding 2000 cfm and the return inlets to the units are not ducted, and pull air into a common mechanical closet where the supply air is not independent, it would require duct smoke detectors. Mechanical room plenums that mix return air from multiple units will spread smoke into all systems.
If the units under 2000 cfm have separately ducted returns to the areas they serve, then they would not be required to have duct smoke detectors. The intent is not to spread the smoke into multiple areas that have supply systems over 2000 cfm.
If the units under 2000 cfm have separately ducted returns to the areas they serve, then they would not be required to have duct smoke detectors. The intent is not to spread the smoke into multiple areas that have supply systems over 2000 cfm.
Commentary
None.