Whitedamp is a noxious mixture of gases formed by the combustion of coal, usually in an enclosed environment such as a coal mine. The main, most toxic constituent is carbon monoxide,[1] which causes carbon monoxide poisoning. Hydrogen sulfide, also called stinkdamp, may co-occur. Coal frequently starts to burn slowly in mines when it is exposed to the atmosphere; partial combustion produces carbon monoxide. The term is etymologically and practically related to terms for other underground mine gases such as firedamp, black damp, stink damp, and afterdamp.