Firedamp

Firedamp is the miners' term applied to light carburetted hydrogen or coal-gas when it issues from crevices in coal-mines (see GAS). These crevices are named 'blowers' by the miners, and are evidently the outlets of gas that exists in a compressed state in pores and cavities in the coal. The issue of the gas is in some cases audible, and on applying a light it burns as a jet of flame. When mixed with air in proportions between $\backslash frac\{1\}\{4\}$ to $\backslash frac\{1\}\{5\}$ of its volume the mixture is explosive, producing disasters that are too well known. The researches of Mr Galloway and others have shown that the gas is only one of the factors producing the worst catastrophes. A comparatively small explosion of gas stirs up any coal-dust that may be lying on ledges, or on the floor of roads and workings, each particle of dust is fired, and the combined result is like the firing of grains of gunpowder.