COURTESY U. S. BUREAU OF MINES
RESCUE PARTY ENTERING MINE AFTER EXPLOSION
THE STORY OF COAL
Safety in Coal Mines
SIX
Since the year 1870, some 60,000 men have lost their lives as a result of coal mining accidents in this country. This is approximately one fatality for every 180,000 tons of coal mined. Gradually this bad record is being improved, thanks to the combined efforts of the United States Bureau of Mines, the mining departments of the various states, the operators and the miners themselves; but coal mining remains a hazardous pursuit.
Falls of the roof are responsible for more accidents than any other single cause. These are likely to occur wherever the roof is not fully timbered; especially in the “rooms,” where the coal is being blasted out. Many accidents also occur in mine shafts, notwithstanding the various safety devices with which the “cage” or elevator is nowadays provided.
Fires and explosions attract a greater amount of public attention than other mining disasters on account of the large number of victims so often involved in a single occurrence of this kind. In the explosion at the Courrières colliery, in France, March 10, 1906, more than 1,100 miners perished. This mine had previously been renowned for its freedom from accidents. Coal mine explosions are due to two principal causes, which may act either separately or in combination—fire-damp and coal-dust. Accumulations of fire-damp, or methane, locked up in the coal seams, are liberated by the removal of the coal. Frequently streams of this gas gush forth with a hissing noise, and are known as “blowers.” Fire-damp is explosive when combined with certain proportions of air. Apart from ventilation, which dilutes the gas below the danger limit, the principal precaution against explosives is the use of safety-lamps, so constructed that the gas cannot come in contact with a naked flame. An excessive amount of coal-dust in the air of the mine may also give rise to explosions. Such explosions may be prevented by wetting the dust, moistening the air, or powdering the walls, roof and floor with a non-explosive “rock-dust.”
After an explosion the air of a mine contains a large amount of the deadly gas carbon monoxide, and this “after-damp,” as it is called, makes rescue work extremely dangerous. Wherever suitable apparatus is available, the rescuers carry with them a supply of oxygen, by breathing which they are able to live for some hours in a poisonous atmosphere. The Bureau of Mines has established a number of rescue stations in the coal-mining districts and maintains several mine safety cars for hurrying rescue crews to the scene of a disaster. The Bureau also instructs the miners in first-aid and rescue work, and is directing a national campaign in behalf of “safety first” in mines.
Of the many methods that have been devised for testing the air of mines for noxious gases none is more interesting than the use of caged canaries. These birds are much more susceptible than human beings to the effects of carbon monoxide, and show signs of distress before a man begins to feel any discomfort from the gas. In many mines they are carried in routine inspections. After an explosion the number of rescuers equipped with oxygen apparatus is always limited. These form the advance guard, and are followed by men without apparatus, who carry canaries, by observing the behavior of which they can tell how far they may safely penetrate into the mine. The Bureau of Mines has devised a special form of cage in which the canary may be revived with oxygen after being overcome with gas. Experiments show that the bird may be asphyxiated and revived again and again without suffering any ill-effects; neither does he acquire an immunity to poisoning which would make him a less reliable indicator.