a mixture of gases (mostly methane) that form in coal mines and become explosive when mixed with air
firedamp详细解释
fire.damp n.（名词）A combustible gas, chiefly methane, occurring naturally in mines from the decomposition of coal.沼气：一种在矿坑里由煤腐烂而自然产生的可燃气体，主要成分是甲烷The explosive mixture of firedamp and air.甲烷和空气的爆炸混合物
