Smoke is a suspension in air (aerosol) of small particles resulting from incomplete combustion of a fuel.
It is commonly an unwanted by-product of fires (including stoves and lamps) and fireplaces, but may also be used for pest control (fumigation), communication (smoke signals), defense (smoke-screen) or inhalation of tobacco or other drugs.
Smoke is sometimes used as a flavouring agent and preservative for various foodstuffs.
Smoke is also sometimes a component of internal combustion engine exhaust gas, particularly diesel exhaust.
Smoke inhalation is the primary cause of death in victims of indoor fires.
The smoke kills by a combination of thermal damage, poisoning and pulmonary irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.