Chemistry of the Safety Match
Safety matches are ‘safe’ because they don’t spontaneously combust. You have to strike them against a special surface in order to get them to ignite. The match heads contain sulfur (sometimes antimony III sulfide [Sb2S3]) and oxidizing agents (usually potassium chlorate [KClO3]), with powdered glass, colorants, fillers, and a binder made of glue and starch. The striking surface consists of powdered glass or silica (sand), red phosphorus, binder, and filler. When you strike a safety match, the glass-on-glass friction generates heat, converting a small amount of red phosphorus to white phosphorus vapor. The phosphorus and potassium chlorate mix in a small amount forming an explosive reaction which ignites due to the friction. The cloud of white smoke and the characteristic smell of burning matches is phosphorus pentoxide (P4O10).