Hydrogen sulfide control on a longwall face

摘要

Exposure to hydrogen sulfide, while mining coal, is potentially hazardous to the health of coal miners. Overexposure to hydrogen sulfide can cause respiratory failure or even death. Acute exposure can rapidly cause a coma with or without convulsions. Hydrogen sulfide has the distinct odor of rotten eggs. This strong, foul-smelling odor can warn miners when they first encounter hydrogen sulfide. Unfortunately, hydrogen sulfide can quickly cause olfactory paralysis. Once this occurs, miners no longer "smell" hydrogen sulfide and will continue working in high concentrations of hydrogen sulfide without realizing it. Moreover, lethal concentrations may not be detected by a victim. The odor threshold for hydrogen sulfide is 0.13 parts per million (ppm). This is far lower than Mine Safety and Health Administration's (MSHA's) Coal Mine Safety and Health's (CMS&H) permissible exposure limit (PEL). CMS&H's PEL is the 1972 American Conference of Governmental Industrial Hygienists Threshold Limit Values (TLV). CMS&H enforces an 8-hour time-weighted-average (TWA_8) of 10 ppm and an Excursion Factor of 2. The Excursion Factor is defined by the ACGIH as the magnitude in level permitted above the TWA_8 for a short time provided the TWA_8 is less than the TLV. In the western United States some coal mines are encountering hydrogen sulfide. The concentrations of hydrogen sulfide can be high. This obligates mine operators to evaluate miners' exposures and control hydrogen sulfide liberations using acceptable and appropriate techniques. This paper describes an engineering evaluation of a multi-faceted approach for controlling hydrogen sulfide exposures. The operator uses a combination of personal monitoring, engineering controls, and work practices to minimize exposure to hydrogen sulfide.