The Ontario Building Code | Configuration
3.2.8.3. Configuration
(1) In buildings constructed in conformance with Articles 3.2.8.4. to 3.2.8.11., the unprotected openings through floor assemblies in an interconnected floor space shall be of sufficient size and shall be positioned relative to each other so as to be capable of containing, within the full height of the interconnected floor space, a cylinder conforming to Sentence (2).
(2) The cylinder referred to in Sentence (1) shall have a cross-section that, where taken at a right angle to the longitudinal axis of such cylinder, is,
(a) a circle at least 9 m in diameter, or
(b) an ellipse at least 7 m wide along the minor axis and at least 65 m2 in area.
In Plain Language
This clause requires smoke venting or a smoke control system for a building containing an interconnected floor space, so smoke doesn't accumulate and spread unchecked between the connected storeys during a fire.
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.