The Ontario Building Code | Combustible Ducts
3.1.5.15. Combustible Ducts
(1) Except as required by Sentence 3.6.4.3.(1), combustibleducts, including plenums and duct connectors, are permitted to be used in a building required to be ofnoncombustible construction provided these ducts and duct connectors are used only in horizontal runs.
(2) Combustible duct linings, duct coverings, duct insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation, vibration isolation connectors, duct tape, pipe insulationhttp://thehandyforce.com/insulation/" title ="Toronto home insulation">insulation and pipe coverings are permitted to be used in a building required to be of noncombustible construction provided they conform to the appropriate requirements of Part 6.
(3) In a building required to be of noncombustible construction, combustibleducts need not comply with the requirements of Part 6 provided the ducts are,
(a) part of a duct system conveying only ventilation air, and
(b) contained entirely within a dwelling unit.
In Plain Language
Combustible ducts (including plenums and connectors) are allowed in noncombustible-construction buildings if used only in horizontal runs, and combustible duct linings, coverings, insulation, vibration isolators, and tape are allowed provided they meet the relevant Part 6 mechanical requirements, with a further exception letting some ducts skip Part 6 entirely under specific conditions.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.