Mine Atmosphere

Mine Atmosphere

 

(mine air), atmospheric air pumped or blown into underground mining excavations; as it passes through the excavations, the air undergoes changes in composition, temperature, and humidity. In comparison with surface atmospheric air, mine air often contains less O2 and more N2 and CO2 because of oxidizing processes and the release of CO2 from rocks. In addition, admixtures of poisonous and explosive gases, vapors, and dust may be present. In normal mine atmospheres, the content of O2 is not less than 20 percent and the content of weakly toxic CO2 is not more than 0.5–1 percent.

The poisonous gaseous vaporous impurities in mine atmospheres include carbon monoxide, nitrogen oxides, hydrogen sulfide, sulfur dioxide, aldehydes, and the gaseous decay products of radioactive substances. Carbon monoxide is formed in blasting, fires, and methane and dust explosions and is present in the exhaust gases of diesel equipment; the maximum permissible concentration in mine atmospheres is 20 mg/m3 (0.0016 percent by volume). Nitrogen oxides are formed in blasting and are present in the exhaust gases of diesel equipment; the maximum permissible concentration is 5 mg/m3 (0.0001 percent) relative to N2O5. Hydrogen sulfide is formed in the decay of wood and the decomposition of pyrites and gypsum by water and is released from deposits of rock salt and pyrite ores; the maximum permissible concentration is 10 mg/m3 (0.00066 percent). Sulfur dioxide is formed when rocks containing sulfur are blasted, when sulfur and sulfide dusts explode, and when fires break out in sulfur and chalcopyrite mines; the maximum permissible concentration is 10 mg/m3 (0.00035 percent). Aldehydes are present in the exhaust gases of diesel equipment; the maximum permissible concentration is 0.7 mg/m3 (0.00008 percent) for acrolein and 0.5 mg/m3 (0.00040 percent) for formaldehyde. Gaseous decay products of radioactive substances—radon and, to a minor extent, thoron and actinon—are released in uranium mines; the maximum permissible concentration of radon is 1.10-11 curie per liter. In addition to these admixtures, mercury and gasoline vapors, heavy hydrocarbons, ammonia, and oil gas are also encountered.

Explosive gaseous and vaporous admixtures may be present in mine atmospheres. Methane, which is released mainly in coal shafts, has a maximum permissible explosion limit of not more than 0.5–2 percent. Hydrogen, which is found mainly in potassium mines, has a maximum permissible content of not more than 0.5 percent. As stated above, gasoline vapors, carbon monoxide, and hydrogen sulfide are both explosive and poisonous, and thus their maximum permissible content is not greater than that permitted by health regulations.

The principal way of maintaining the purity of mine atmospheres is ventilation. During the cold period of the year, atmospheric air introduced into shafts is heated. To reduce the temperature of mine atmospheres, artificially cooled air is used.

REFERENCES

Komarov, V. B., and Sh. Kh. Kil’keev. Rudnichnaia ventiliatsiia, 2nd ed. Moscow, 1969.
Burchakov, A. S., P. I. Mustel’, and K. Z. Ushakov. Rudnichnaia aerologiia. Moscow, 1971. Sanitarnye normy proektirovaniia promyshlennykh predpriiatii: SN245–71. Moscow, 1972.

K. Z. USHAKOV and S. IA. KHEIFITS

References in periodicals archive ?
When cold weather causes barometric pressure to drop, methane gas can migrate more easily into the mine atmosphere, increasing the risk of an explosion.
DPM behaves similarly to surrounding gases, she said, but has longer residence times in a mine atmosphere.
Vybuchovy trojuhelnik": A software tool for evaluation of explosibility of coal mine atmosphere.
continuous measurements of the temperature of the mine atmosphere (2 points),
Key to the device is its mass sensor, the Tapered Element Oscillating Microbalance (TEOM), which continuously measures the mass of particles from the mine atmosphere onto a sample filter, resolving masses down to 1 [micro]g.
The thicker the layer of shotcrete that is applied, the more it reduces the gamma radiation given off to the mine atmosphere.
Before miners are allowed to go back into areas after blasting, the mine atmosphere must be shown to be safe from S|O.
Tenders are invited for devices, systems, means controlfor parameters of the mine atmosphere and degassing
Hydrophobic rock dust so far has been applied in a dry fashion, adding to the respirable dust count in the mine atmosphere.
The only safety requirements are monthly determinations of Hg in the waste and of Hg vapor in the mine atmosphere.

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