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 can trigger explosions. Historically, if such a pocket was highly pressurized, it was termed a "bag of foulness".

Coal dust is a fine-powdered form of coal which is created by the crushing, grinding, or pulverization of coal rock. Because of the brittle nature of coal, coal dust can be created by mining, transporting, or mechanically handling it.