The Ontario Building Code | Access Openings
6.2.1.11. Access openings="http://thehandyforce.com/windows/" title ="Window installer in Toronto">openings
(1) Any covering of an access opening through which a person could enter shall be openable from the inside without the use of keys where there is a possibility of the opening being accidentally closed while the system or equipment is being serviced.
In Plain Language
Any covering of an access opening large enough for a person to enter must be openable from the inside without special tools, so someone working inside a mechanical space can't become accidentally trapped.
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.