blackdamp (also known as stythe or choke damp) is an asphyxiant, reducing the available oxygen content of air to a level incapable of sustaining human or animal life. it is not a single gas but a mixture of unbreathable gases left after oxygen is removed from the air and typically consists of nitrogen, carbon dioxide and water vapour. the suffix "damp" is believed to derive from the german word for vapours (""dampf""). the word "damp" is used in similar mining terms such as white damp, fire damp and stink damp.