There are two methods: (1) Long holes are drilled parallel to the coal face. Charges of Hydrobel explosive are spaced along the holes and fired under water pressure. The object is to loosen the coal and allay the dust along the entire face in one operation. See also pulsed infusion shot firing about 40 ft (12.2 m) long in the line of advance of the workings. The holes are not charged with explosive and fired but only subjected to water pressure up to 3,000 psi (20.7 MPa) to loosen the coal and allay the dust in the cleats. The holes may be drilled during weekends and of a length about equal to the weekly advance of the face.