All mines generating fire damp shall be kept free of standing gas in all working places and roadways. No accumulation of explosive gas shall be allowed to exist in the worked-out or abandoned parts of any mine. It shall be removed as soon as possible after its discovery, and no miners or other persons who are not employed in the removal of the dangerous accumulation, shall be allowed to remain in any mine, or part of mine, during the time that a dangerous accumulation of explosive gas is being removed from any part of the mine, and the entrance or entrances to be worked out and abandoned places, shall be properly fenced off and cautionary notices shall be posted upon said fencing to warn persons of danger.