The Ontario Building Code | Light Diffusers and Lenses
3.1.13.4. Light Diffusers and Lenses
(1) The flame-spread rating of combustible light diffusers and lenses in all occupancies other than Group A, Division 1 is permitted to be more than the flame-spread rating limits required elsewhere in this Subsection, provided the light diffusers and lenses,
(a) have a flame-spread rating not more than 250 and a smoke developed classification not more than 600 when tested in conformance with CAN/ULC-S102.2, "Test for Surface Burning Characteristics of Flooring, Floor Coverings, and Miscellaneous Materials and Assemblies",
(b) fall to the bottom of the test apparatus before igniting when tested in conformance with ULC-S102.3, "Fire Test of Light Diffusers and Lenses",
(c) are not prevented from falling from the ceiling by construction located beneath the elements, and
(d) are not used in a corridor that is required to be separated from the remainder of the buildingby a fire separation or in an exitshaft unless individual diffusers or lenses are not more than 1 m2in area and are not less than 1.2 m apart.
In Plain Language
Combustible light diffusers and lenses (outside Group A, Division 1 occupancies) can exceed the usual flame-spread limits provided they meet specific alternate criteria: a 250 flame-spread rating, 600 smoke-developed classification under CAN/ULC-S102.2 testing, and behavior (like falling away) described further in the 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.