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 insulation, vibration isolation connectors, duct tape, pipe 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.