This is an important consideration because requirements concerning smoke production from lining materials have been introduced into the NBC 1970 when such materials are used in high rise buildings, as already mentioned. Because, until very recently, the number of E84 ratings in the 75 to 200 range in the relevant literature and UL listings was limited, particularly on Canadian products, it has been the objective of the Division to produce and publish information on conventional lining and coating materials as rapidly as possible. Low Density Fibreboards Fibreboard ceiling tiles and panelling, whether factory-finished or painted on site, have often been considered almost explosively flammable, because of their involvement in many fatal fires in the past. European research has certainly suggested that painted fibreboard linings contribute to early flashover because of their ready ignitability and their insulating properties. A substantial tonnage of foreign hardboard is imported into Canada for subsequent finishing or use in furniture manufacture.
Little information is available on the effect of latex paints or primers.
Particleboards Particleboards, like hardboards, are produced in a wide variety of types, densities and thicknesses, from many different raw materials, virgin or by-product, and for distinctly different markets. Boards of homogeneous and graduated construction have been produced for furniture, subflooring, decorative panelling, sheathing and plywood core stock. The fire hazard classifications of the more common structural plywoods have been adequately covered in the literature. Lack of uniformity of contact between the thin plywood and the massive cover of the furnace, indeterminate effects of the exposed joints, and inherent variability in the plywood itself have resulted in poor agreement between runs on supposedly identical panels. Evaluation of such plywoods which have been coated with opaque fire-retardant paints in an attempt to reach an FSC of 150 has proved to be difficult.