Explosion in a Coal Mine
Circulation of fresh air was critical in coal mining. In spite of passages created to control this, ther were always side rooms through which no circulation could be effected. These areas were where explosive “fire-damp", or light carbide of hydrogen, evolved spontaneously from the coal, and often caused fatal accidents to the miners.
Winchell, Alexander Sketches of Creation (New York, NY: Harper & Brothers, 1870)