This one is about smoke detectors and the 2000 cfm ratings.
Over the last 30 years I have heard many different interpretations of this code and it's requirements. I am hoping someone can shed some light or have more insight.
If you have 2 air handling units in a common area and their combined capacity is over 2000 cfm do they need smoke detectors?
Can a room be considered a common return air plenum?
Then there is the exception:Smoke detectors shall not be required where air distribution systems are incapable of spreading smoke beyond the enclosing walls, floors and ceilings of the room or space in which the smoke is generated.
I have had a state fire marshal explain to me that this "spreading of smoke" can be done by an isolated return in a room that is separated from the main service area.Therefore a detector is required.

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