3.6.4.

(1) This Subsection applies to horizontal service spaces and service facilities, including ceiling spaces, duct spaces, crawl spaces and attic or roof spaces.

(1) A horizontal service space that penetrates a required vertical fire separation shall be separated from the remainder of the building it serves in conformance with Sentence (2).

(2) If a horizontal service space or other concealed space is located above a required vertical fire separation other than a vertical shaft, this space need not be divided at the fire separation as required by Article 3.1.8.3. provided the construction between this space and the space below is a fire separation with a fire-resistance rating equivalent to that required for the vertical fire separation, except that the fire-resistance rating is permitted to be not less than 30 min if the vertical fire separation is not required to have a fire-resistance rating more than 45 min.

(1) A concealed space used as a plenum within a floor assembly or within a roof assembly need not conform to Sentence 3.1.5.15.(1) and Article 6.2.3.2. provided,

(a) all materials within the concealed space have a flame-spread rating not more than 25 and a smoke developed classification not more than 50, except for,

(i) tubing for pneumatic controls,

(ii) optical fibre cables and electrical wires and cables that exhibit a flame spread not more than 1.5 m, a smoke density not more than 0.5 at peak optical density and a smoke density not more than 0.15 at average optical density when tested in conformance with the Flame and Smoke Test in the Appendix to CAN/CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables” (FT6 Rating),

(iii) optical fibre cables and electrical wires and cables that are located in totally enclosed noncombustible raceways,

(iv) totally enclosed nonmetallic raceways that exhibit a horizontal flame distance of not more than 1.5 m, an average optical smoke density of not more than 0.15, and a peak optical smoke density of not more than 0.5 when tested in conformance with the Test for Flame Propagation and Smoke Density Values in Section 3.3 of the ULC/ORD-C2024, “Fire Tests for Optical Fibre Cable Raceway” (FT-6 Rating), and

(v) single conductor electrical wires and cables that exhibit a vertical char of not more than 1.5 m when tested in conformance with the Vertical Flame Test —Cables in Cabletrough in Clause 4.11.4. of CSA C22.2 No. 0.3, “Test Methods for Electrical Wires and Cables” (FT4 Rating), and

(b) the supports for the ceiling membrane are of noncombustible material having a melting point not below 760°C.

(2) If a concealed space referred to in Sentence (1) is used as a return-air plenum and incorporates a ceiling membrane that forms part of the required fire-resistance rating of the assembly, every opening through the membrane shall be protected by a fire stop flap that shall,

(a) stop the flow of air into the concealed space in the event of a fire,

(b) be supported in a manner that will maintain the integrity of the ceiling membrane for the duration of time required to provide the required fire-resistance rating, and

(c) conform to CAN4-S112.2-M, “Fire Test of Ceiling Firestop Flap Assemblies”.

(3) Asbestos paper shall not be exposed in supply and return-air systems.

(1) An attic or roof space more than 600 mm high shall be provided with access from the floor immediately below by a hatchway not less than 550 mm by 900 mm or by a stairway.

(1) A horizontal service space, consisting of ceiling and duct spaces, that is more than 1 200 mm high and 600 mm wide shall have inspection doors not less than 300 mm in both horizontal and vertical dimensions placed so that the entire interior of the duct or space can be viewed.

(1) A crawl space shall have at least one access opening not less than 550 mm by 900 mm.