The ability of a solid chemical to ignite, to burn rapidly, or for the flame to spread quickly is a potentially dangerous physical hazard. These chemicals can burn so vigorously or persistently that they create a serious fire hazard. Classification as a flammable solid differentiates between solid chemicals that can be ignited and those that burn rapidly, or whose burning behavior is particularly dangerous. Only solid chemicals whose burning rate exceeds a certain value are classified as flammable solids. Various solid organic chemicals meet the criteria to be classified as flammable solids. For inorganic solids, classification as a flammable solid is less frequent.
Flammable solid means a solid which is a readily combustible solid, or which may cause or contribute to fire through friction.
Readily combustible solids are powdered, granular, or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.