Smoke is a collection of airborne solidand liquid particulatesand gases emitted when a material undergoes combustionor pyrolysis, together with the quantity of air that is entrainedor otherwise mixed into the mass. It is commonly an unwanted by-productof fires (including stoves, candles, oil lamps, and fireplaces), but may also be used for pest control( fumigation), communication ( smoke signals), defensive and offensive capabilities in the military ( smoke-screen), cooking, or smoking( tobacco, cannabis, etc.). Smoke is used in rituals where incense, sage, or resin is burned to produce a smell for spiritual purposes. Smoke is sometimes used as a flavoring agent, and preservative for various foodstuffs. Smoke is also a component of internal combustion engine exhaust gas, particularly diesel exhaust. Smoke inhalationis the primary cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, poisoningand pulmonaryirritation caused by carbon monoxide, hydrogen cyanide and other combustion product.