It shall be the duty of the mine foreman, assistant mine foreman or fire boss to examine all working places under his or her supervision for hazards at least once every two hours during each coal-producing shift, or more often if necessary for safety. In all mines such examinations shall include tests with an approved detector for methane and oxygen deficiency.  It shall also be his or her duty to remove as soon as possible after its discovery any accumulations of explosive or noxious gases in active workings, and where practicable, any accumulations of explosive or noxious gases in the worked out and abandoned portions of the mine. It shall be the duty of the mine foreman, assistant mine foreman or fire boss to examine each mine within three hours prior to the beginning of a shift and before any miner in such shift enters the active workings of the mine.