Blackdamp

Blackdamp (also known as stythe or choke damp), sometimes found in enclosed environments such as mines, sewers, wells, tunnels and ships' holds, is an asphyxiant, reducing the available oxygen content of air to a level incapable of sustaining human or animal life.

[citation needed] Blackdamp is considered a particularly pernicious type of damp (especially in a historical context), due to its omnipresence where exposed coal is found, and slow onset of symptoms.

Many of the initial symptoms of oxygen deprivation (dizziness, light-headedness, drowsiness and poor coordination) are relatively innocuous and can easily be mistaken for simple fatigue, given the physically strenuous job of coal mining.

[2] The gas mixture has been responsible for many deaths among underground workers, especially miners—for example, the 1862 Hartley Colliery disaster, when 204 men and boys were trapped when the beam of an engine suddenly broke and fell down the single shaft, damaging the ventilation system and blocking it with debris.

In active mining operations, the threat from blackdamp is addressed with proper mineshaft ventilation as well as various detection methods, typically using miners' safety lamps or hand-held electronic gas detectors.