1. Miner wearing a type N gas mask and observing a flame safety lamp.. 2. Diagram showing parts of a type N gas mask with arrows pointing 3. Interior of the face piece of a type N gas mask showing rubber tubes that lead dry incoming air over the eyepieces to prevent fogging____ 9. Crew of oxygen-apparatus men and gas-mask crew entering a mine.. 21 10. Crews with gas masks and oxygen apparatus at a fresh-air base in a II The miners' gas mask was developed at the time of and since the World War, and in comparatively recent years it has had an important place in mine rescue and recovery work during fires and after explosions. The mask as used in mines is principally a protection against carbon monoxide, the most dangerous poisonous gas from fires, and against other gases, such as sulphur gases, which may arise from fires. As it protects against all classes of poisonous gases in air and against smoke, it is designated according to Bureau of Mines classification as "type N." The gas mask aids the work conducted with the oxygen breathing apparatus, but it can never replace the Oxygen breathing apparatus, because the gas mask is only a filter capable of protecting against limited amounts up to 2 or 3 per cent of poisonous gases in air otherwise good to breathe. Everybody must breathe oxygen to live. 21 volumes in every 100 volumes of air, or 79 per cent of air is mostly nitrogen gas. after mine explosions, the oxygen content of the air in mines may be reduced from the normal 21 per cent to such small quantities that the air will no longer support a man's life. This lack of oxygen may not occur throughout the mine, but there may be a deficiency of oxygen in sections, especially in return airways and in openings in the neighborhood of fire or regions traversed by mine explosions. Fires confined in unventilated mine areas always deplete the oxygen to some extent, and as the gas mask does not supply oxygen, it can not protect against atmospheres too low in oxygen. Oxygen constitutes nearly 21 per cent; the remaining When fires are burning or LIMITATIONS OF USE OF TYPE N, MINERS' GAS MASK Oxygen breathing apparatus are made to carry a supply of compressed oxygen for wearers to breathe and enable them to work in an atmosphere regardless of its oxygen content. The gas masks may 'Manuscript completed June, 1928. 'Katz, S. H., Bloomfield, J. J., and Fieldner, A. C., The Universal and the Fireman's Gas Masks: Tech. Paper 300, Bureau of Mines, 1923, 22 pp. |