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 ?
This approval came after a thorough evaluation of the Mine atmosphere by Foresight, MSHA, and IDNR officials.
Tenders are invited for devices, systems, means controlfor parameters of the mine atmosphere and degassing
Before miners are allowed to go back into areas after blasting, the mine atmosphere must be shown to be safe from S|O.
As a result of these efforts, the mine atmosphere was rendered inert, or without oxygen, and the Excel No.
Analysis of the continuous mine atmosphere readings that the team has been taking indicates that gas levels remain steady and oxygen levels continue to decrease.
Once the remote seal construction was completed and the mine atmosphere behind the seals was rendered inert (without oxygen), mine rescue personnel from MSHA, KDMM, and Alliance's White County Coal, LLC, Gibson County Coal, LLC, and Warrior Coal, LLC subsidiaries entered the mine, restored ventilation and constructed thirty-two permanent seals effectively extinguishing the mine fire and totally isolating the affected area of the mine behind these seals.
I am hopeful that MSHA will use strong and effective measures to cause coal mines to reduce the level of respirable dust in the mine atmosphere to a level of personal exposure, which will prevent new incidences of respiratory disease and the further development of such disease in any miner.
After installation of an initial set of temporary seals from the surface and injection of nitrogen and carbon dioxide gases effectively isolated the fire and rendered the mine atmosphere inert (that is, without oxygen), Webster County Coal re-entered the mine late last week.
Gas samples taken by MSHA from the Bandytown ventilation fan show the mine atmosphere experienced a rapid inundation of methane, raising the concentration in the ventilation air significantly.
Some of the potential markets for Cemtrex water quality monitors include Fluorescent Lamp Recycling, Precious Metals & Mine Atmosphere, Natural Gas Processing, and Hydrogen Chloride (HCl) Manufacturing Plants, just to name a few.
In late November 2007, in response to a safety agency requirement, the mine was sealed as a final step before re-entry in order to ensure that the mine atmosphere was inert and incapable of supporting combustion.
The company has established more than 100 monitoring stations, allowing the mine atmosphere to be thoroughly sampled.

Full browser ?