This, then, is the line of first defence against fire in buildings. Flammable liquids and gases are special cases and there are provisions for controlling their location. In general, however, it is difficult to predict where combustible materials might be located, particularly in large buildings. Even buildings constructed of non-combustible materials will almost without exception contain materials that burn under certain circumstances. On the other hand, materials that are designated combustible according to tests may be of negligible significance in fires.
Wood is a good example of a common material for which fire performance is difficult to predict.
It may also ignite, however, at much lower temperatures if the time of exposure to heat is longer. Table 1 defines the terms that are commonly used to describe the ignition process and its various aspects. The initiation of sustained combustion. Combustibility The propensity of a material to burn. A material des defined as combustible if it raises the temperature of the furnace interior by 30 C deg or more when it burns.