The Ontario Building Code | Heat Circulating Duct Openings
9.22.9.4. Heat Circulating Duct openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings
(1) The clearance of combustible material above heat circulating duct openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings from those openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings shall be not less than,
(a) 300 mm where the combustible material projects not less than 38 mm from the face, and
(b) 150 mm where the projection is less than 38 mm.
9.22.10. fireplace Inserts and Hearth-Mounted Stoves
In Plain Language
Heat circulating duct openings, used in fireplaces designed to distribute warm air, must meet the requirements set out in this article.
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.