爆発ガス

Also known as mine gas, coal mine gas, fire damp

Firedamp is any flammable gas found in coal mines, typically coalbed 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 of the gas can cause explosions. Historically, if such a pocket was highly pressurized, it was termed a "bag of foulness".