Take a Make-Up Air Unit (MAU) if over 2,000 CFM. NFPA 90A would mean the unit should have a duct smoke detector installed to automatically shut the unit down. (It seems to be the only exemption to the need for Duct Smoke Detector is Exhaust Fan (22.214.171.124), however, IMC 606.1 Controls required. Air distribution systems shall be equipped with smoke detectors listed and labeled for installation in air distribution systems 606.2 Where required. Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3. 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.
So, what do I go with?