9.33.6.4.Coverings, Linings and Insulation

(1) Reserved. (2) Reserved. (3) Reserved. (4) Reserved. (5) Except as permitted in Sentences (6) and (7), foamed plastic insulation shall not be used as part of an air duct or for insulating an air duct. (6) Foamed plastic insulation conforming to Article 9.25.2.2. is permitted to be used to insulate a galvanized steel, stainless steel or aluminum air duct, provided (a) the foamed plastic insulation applied to supply ductwork is not less than 3 m from the furnace bonnet, (b) the temperature within the ductwork where the insulation is installed is not greater than 50°C, (c) duct joints are taped with a product conforming to Sentence 9.33.6.3.(1), (d) return air plenums are separated from the foamed plastic insulation, and (e) the foamed plastic insulation is protected in accordance with Article 9.10.17.10. (7) Foamed plastic insulation is permitted to be used in a ceiling space that acts as a return air plenum provided the foamed plastic insulation is protected from exposure to the plenum in accordance with Sentence 3.1.5.14.(4). (8) Reserved. (9) Linings of ducts shall be installed so that they will not interfere with the operation of volume or balancing dampers or of fire dampers, fire stop flaps and other closures.