Mine Ventilation

Operations incident to supplying fresh air, and removing vitiated air in mines. In metal mines, especially when open to the surface at different levels, the natural current caused by the difference in temperature between the outer and inner air is usually sufficient for the purpose. In coal mines and others, in which dangerous gases are met, resort is had to artificial ventilation, whereby a current of fresh air is made to traverse the workings, either by increasing mechanically the pre ure in the downcast shaft, or by reducing the pre ure in the upcast, the reduction being brought about either mechanically or by the aid of a furnace placed at or near the bottom of the upcast.