Sentence Examples


  • In a mine with shafts opening at the same level, natural ventilation once established will be effective during cold weather, as the downcast will have the temperature of the outside air, while the upcast will be filled with the warm air of the mine.
  • So far as possible, vitiated air is led directly to the shaft instead of passing through other workings; for example, mine stables when used are placed near the upcast shaft and ventilated by an independent split of the ventilating current.
  • The use of two independent connexions - whether separate pits or sections of the same pit, between the surface and the workings - is necessary for the service of the ventilation, fresh air from the surface being carried down one, known as the " downcast," while the foul or return air of the mine rises through the other or " upcast " pit back to the surface.
  • This is effected by carrying through the workings a large volume of air which is kept continually moving in the same direction, descending from the surface by one or more pits known as intake or downcast pits, and leaving the mine by a return or upcast pit.
  • Such a circulation of air can only be effected by mechanical means when the workings are of any extent, the methods actually adopted being - (i) The rarefaction of the air in the upcast pit by a furnace placed at the bottom; and (2) Exhaustion by machinery at the surface.

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