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| Propeller fans installed in a large-opening mine |
Background
Continuing and emerging air quality issues in meta-nonmetal mines deal with the presence of silica dust, diesel particulate matter (DPM), noxious gases (from diesel equipment, cutting and welding, and production blasts), and the lack of visibility due to fog. A study by the Mine Safety and Health Administration (MSHA) in 2003 found that nearly 22% of metal mines and over 16% of stone mines in the United States had air samples that exceeded the DPM regulatory limit of 400 µg/m3 total carbon. Underground stone miners are frequently exposed to respirable crystalline silica dust in addition to DPM. Chronic overexposure to silica dust can lead to silicosis, a progressive, irreversible condition caused by deposition of silica dust in lung tissues. Analysis of MSHA’s compliance dust-sampling data collected from 1993 to 1998 showed that 15% of the dust samples from underground stone mines exceeded the permissible exposure limit (PEL) for silica dust. Certain occupations, namely truck drivers, crusher operators, front-end loader operators, and rotary drill operators, had a higher risk of exposure and, on average, 20% to 25% of the samples exceeded the PEL.
These issues are of particular importance in mines with large openings. However, these contaminants can be effectively reduced by using engineering controls such as cleaner engines and filters and proper ventilation methods. Adequate ventilation in these mines generally requires a combination of large air quantities and effective planning and placement of ventilation control devices, such as auxiliary fans and stoppings.
Potential Outcome
This project will lead to the use of flexible ventilation stoppings and various auxiliary fan types to increase face ventilation efficiencies. Highly efficient mine ventilation layouts will improve the delivery of ventilation airflow to the working face, thereby reducing worker exposure to airborne contaminants. By 2009, a comprehensive toolbox of ventilation guidelines in the form of a ventilation design handbook for large-opening underground mines will be available. These guidelines will lead to a significant increase in the percentage of large-opening mines that use a highly efficient, engineered ventilation system that provides improved air quality to miners.