Combustible light diffusers and lenses in all occupancies other than Group A, Division 1, where the light diffusers and lenses:

• 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,”
• fall to the bottom of the test apparatus before igniting when tested in conformance with ULC S102.3-M, “Fire Test of Light Diffusers and Lenses,”
• are not prevented from falling from the ceiling by construction located beneath the elements, and
• are not used in a corridor that is required to be separated from the remainder of the building by a fire separation or in an exit shaft unless individual diffusers or lenses are not more than 1 m² in area and are not less than 1.2 m apart.

This applies to buildings described in Sentence 1.3.3.2.(1) of Division A, and to buildings to which Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9] as stated in Sentence 9.10.17.8.(1).

Exceptions: 

To exempt light diffusers and lenses from the application of Sentence 3.1.5.1.(1), which would otherwise require the diffusers and lenses to be of noncombustible construction, and Sentences 3.1.13.2.(1) and 3.1.13.6.(5), which would otherwise require a lower maximum flame-spread rating, if certain conditions are met, on the basis that these building elements will not significantly contribute to the spread of flame.