Where coal seams are worked by the longwall method it is necessary to maintain roadways leading to the face. These roadways should be of sufficient height to permit the easy passage of workers and materials, and this invariably means that some of the stone above the coal must be removed. This operation is known as ripping, and, unless the roof strata are very soft, blasting will be required. The main considerations in ripping blasting are to keep the sides of the roadway square, and to obtain good fragmentation of the stone so that it can be removed easily.