The Ontario Building Code | Fire-Retardant Treated Wood

3.1.4.5. Fire-Retardant Treated wood

(1) If fire-retardant treated wood is specified in this Part, the wood shall,

(a) be pressure impregnated with fire-retardant chemicals in conformance with CAN/CSA-O80 Series-M, "wood Preservation", and

(b) have a flame-spread rating not more than 25.