Firedamp

Firedamp is flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane. It is particularly found in areas where the coal is bituminous. The gas accumulates in pockets in the coal and adjacent strata, and when they are penetrated, the release can trigger explosions. Historically, if such a pocket was highly pressurized, it was termed a "bag of foulness".

Damps is the collective name given to all gases (other than air) found in coal mines in Great Britain. The word corresponds to German Dampf, the name for "vapour".

Alongside firedamp, other damps include blackdamp (carbon dioxide and other gases), poisonous, explosive stinkdamp (hydrogen sulfide), with its characteristic "rotten egg" odour, and the insidiously lethal afterdamp (carbon monoxide and other gases) produced following explosions of firedamp or coal dust.

Firedamp is explosive at concentrations between 4% and 16%, with most explosions occurring at around 10%. It caused much loss of life in coal mines before the invention of the Geordie lamp and Davy lamp. The invention was prompted by the Felling mine disaster near Newcastle upon Tyne claiming 92 lives on 25 May 1812. Davy experimented with iron gauze, determining the maximum size of the gaps and the optimum wire thickness to prevent a flame passing through the gauze. If a naked flame was thus enclosed totally by such a gauze, then methane could pass into the lamp and burn safely above the flame. He did not patent his invention.

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