18-28-606.2.2 Common supply and return air systems.

   Where multiple air-handling systems share common supply or return air ducts or plenums with a combined designed capacity greater than 2,000 cfm (0.9 m 3 /s), the return air system shall be provided with smoke detectors in accordance with Section 18-28-606.2.1.

   Exception: Individual smoke detectors shall not be required for each variable air volume (VAV) zone unit or VAV-type fan-powered terminal unit, provided that such units do not have an individual design capacity greater than 2,000 cfm (0.9 m3/s) and will be shut down by activation of one of the following:

      1.   Smoke detectors required by Sections 18-28-606.2.1 and 18-28-606.2.3.

      2.   An approved area smoke detector system located in the return air plenum serving such units.

      3.   An area smoke detector system as prescribed in the exception to Section 18-28-606.2.1.

   In all cases, the smoke detectors shall comply with Sections 18-28-606.4 and 18-28-606.4.1.