30 CFR § 57.22104 Open flames (I-C mines). (a) Open flames, including cutting and welding, shall not be used
underground. (b) Welding and cutting shall not be done within 50 feet of a mine
opening unless all persons are out of the mine and the mine opening is
covered. The cover shall be a substantial material, such as metal or wood,
topped with a layer of wetted material to prevent sparks and flames from
entering the mine opening.