The rate at which flame spreads on the exposed interior surfaces or a room or space can have an impact on the rate of fire growth within an area, especially if the materials of the exposed surfaces are highly flammable. Therefore, the National Building Code of Canada (NBC)¹ regulates the surface flammability of any material that forms part of the interior surface of walls, ceilings and, in some cases, floors, in buildings. Based on a standard fire-test method, the NBC uses a rating system to quantify surface flammability that allows comparison of one material to another, and the ratings within that system are called flame-spread ratings (FSR).

For some buildings, the smoke generated by materials or products lining some areas of the building when they burn is also regulated by the NBC. Since it may take some additional time for occupants to exit the building, this applies to all unsprinklered high buildings and all elevators or Group B occupancies in high buildings. The FSR and SDC is also regulated for some materials used in ducts and plenums. The smoke produced from a material or product is measured and quantified through another rating system, based on a standard fire-test method — the smoke developed classification (SDC). For most wood products used as interior finishes, both of these properties — the FSR and the SDC — are to be determined in accordance with CAN/ULC-S102, “Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies.”² For flooring, CAN/ULC-S102.2 “Standard Method of Test for Surface Burning Characteristics of Flooring, Floor Coverings, and Miscellaneous Materials and Assemblies is to be used when a SDC or FSR is required.