18-28-602.2.1 Materials exposed within plenums.

   Materials exposed within plenums shall be noncombustible or shall have a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84. No floor drains or sanitary waste and vent piping, storm drain piping or condensate drain piping may be exposed within a supply plenum. No material which has the potential of contaminating the air stream may be located in a supply plenum.

   Exceptions:

      1.   Rigid and flexible ducts and connectors shall conform to Section 18-28-603.

      2.   Duct coverings, linings, tape and connectors shall conform to Sections 18-28-603 and 18-28-604.

      3.   This section shall not apply to materials exposed within plenums in one- and two-family dwellings.

      4.   This section shall not apply to smoke detectors.