Smoke is a suspension in air of small particles resulting from incomplete combustion of a fuel. It is commonly an unwanted by-product of fires, but may also be used for pest control, communication (smoke signals) or inhalation. Controlled combustion normally takes place in closed containers (such as engines, stoves and lamps) and the exhaust smoke is released through a chimney or exhaust pipe.

Smoke inhalation is a common cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, asphyxiation and pulmonary irritation.

See also dust, fire fighter, smog, tobacco.