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of ,methane gas from the coal seams . The mines are ventilated <br /> using an exhaust type system. The exhaust fans create negative <br /> pressure on the mine that causes the air to course in through the <br /> intakes, across the faces, and out the returns . Air is directed <br /> to the faces by means of temporary and permanent stoppings , <br /> overcasts and brattice cloth line curtains . The main fans are <br /> located on the surface in fireproof housing and are connected to <br /> the mine shafts by metal ducts . The installations are in accord- <br /> ance with MSHA standards and regulations . <br /> (b) Roof control <br /> Mid-Continent utilizes roof bolts, <br /> timbers , arches and cribs to stabilize mine roofs in the areas <br /> where the room and pillar mining method is used . Where the <br /> longwall mining method is used, roof stability is attained by the <br /> hydraulic longwall face supports, gate supports , arches, cribs, <br /> packwalls and roof bolts . <br /> (c) Dust control <br /> The purposes of suppressing coal dust in <br /> underground mine workings are to protect the miners from respi- <br /> ratory illnesses and to eliminate the possiblity of coal dust <br /> explosions . Mid-Continent utilizes a combination of ventilation, <br /> water spray, cleanup, and rock dusting to reduce the airborne <br /> coal dust in the ventilating air current at safe levels and to <br /> prevent dangerous accumulations of coal dust . In general terms, <br /> the procedures that are followed include the expeditious removal <br /> of loose and pulverized coal from the mine, maintaining ventila- <br /> tion at the working faces that draws dust away from the miners, <br />