The Ontario Building Code | Size of Chimney Flues
184.108.40.206. Size of Chimney Flues
(1) Except for chimneys serving fireplaces, the size of a chimney flue shall conform to the requirements of the solid fuel-burning applianceinstallation standard referenced in Sentence 220.127.116.11.(1) and Article 18.104.22.168.
(2) Where a chimney flue serves only one solid fuel-burning appliance, the flue area shall be at least equal to that of the flue pipeconnected to it.