# Engineering Controls Database

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## Best Practices for Dust Control in Coal Mining – Continuous Mining Operations – Exhausting Face Ventilation

| Problem:                | Respirable dust exposure has long been known to be a serious health threat to workers in many industries. In coal mining, overexposure to respirable coal mine dust can lead to coal workers’ pneumoconiosis (CWP). CWP is a lung disease that can be disabling and fatal in its most severe form. In addition, miners can be exposed to high levels of respirable silica dust, which can cause silicosis, another disabling and/or fatal lung disease.  Exposure to coal mine dust may also increases a miner’s risk of developing chronic bronchitis, chronic obstructive pulmonary disease, and pathologic emphysema. Once contracted, there is no cure for CWP or silicosis. The goal, therefore, is to limit worker exposure to respirable dust to prevent development of these diseases.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| What this means to you: | CWP contributed to the deaths of 10,406 U.S. miners during 1995–2004 [NIOSH 2008].  Pneumoconiosis continues to be a very serious health threat to underground coal mine workers.The velocity and quantity of face ventilating air are important factors for controlling respirable dust exposure of the continuous miner operator. A good ventilation plan consists of sufficient mean entry air velocity to confine dust near the face and/or direct it toward the return entry with high enough quantity for diluting generated respirable dust. The two ventilation schemes most widely used for underground coal mining are blowing and exhausting. There are advantages and disadvantages to both systems as they relate to face worker dust exposure.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| Description of control: | Exhausting Face Ventilation.  When exhausting ventilation is used, intake air is delivered to the face in the working entry. The clean air sweeps the face, and the dust-laden air is then drawn behind the return curtain or through the exhaust tubing to the return entries. This system will keep mobile equipment in fresh air and affords the continuous miner operator more freedom of movement than a blowing ventilation system. In addition, exhausting ventilation allows more visibility around the loading area so that shuttle car operators can easily determine where the continuous miner operator is located when entering the face area. The following best practices will reduce dust exposure on exhausting ventilation sections: •	Figure 1 shows a schematic of an exhaust ventilation system. Exhausting airflow allows for more flexibility than blowing, giving the operator more options to avoid dusty air. However, MSHA maintains that position A (opposite side of curtain) is preferred from a dust control perspective. As always, good communication between the continuous miner operator and shuttle car operators is essential for safe positioning.•	An advantage of exhausting ventilation is that shuttle car operators are always positioned in fresh air.•	At a minimum, the air quantity reaching the inby end of the line curtain should be equal to the scrubber capacity to guard against recirculation of air.  Unlike blowing ventilation, there is no restriction on the upper limit of face air quantity with exhausting ventilation.  Face airflow quantity should be determined with the scrubber off.•	MSHA regulations state that mean entry air velocity must be at least 60 ft/min when using exhaust ventilation systems.•	The end of the exhaust curtain or tubing must be kept within 10 ft of the face when not using a scrubber to ensure that air reaches and effectively sweeps the face.•	The operator should not proceed inby the end of the line curtain since this will expose the operator to dust-laden return air. If operator dust levels are too high, the first thing to check is whether the operator is standing parallel to or outby the end of the line curtain [Kissell and Goodman 2003].•	Scrubber exhaust must be on the same side of the entry as the line curtain/tubing to allow scrubber exhaust to discharge directly into return air [Colinet and Jankowski 1996].**Figure 1 - Schematic of an exhaust ventilation system**               |
| References:             | NIOSH [2010]. Information circular 9517. Best practices for dust control in coal mining. Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-110.Colinet JF, Jankowski RA [1996]. Dust control considerations for deep-cut faces when using exhaust ventilation and a flooded-bed scrubber. In: Transactions of Society for Mining, Metallurgy, and Exploration, Inc. Vol. 302. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc., pp. 104–111.Kissell FN, Goodman GVR [2003]. Continuous miner and roof bolter dust control. In: Kissell FN, ed. Handbook for dust control in mining. Pittsburgh, PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2003-147, IC 9465, pp. 23– 38. NIOSH [2008]. Work-related lung disease surveillance report, 2007. Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2008143a.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Keywords:               | coal minerscoal miningcontinuous mining machinecontinuous mining machine operatorminingunderground mines                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |

November 16, 2018
National Institute for Occupational Safety and Health