In all mines wherein explosive gas is generated, and also in all mines where the fire damp has generated, in sufficient quantities to be detected by the ordinary safety lamp, every working place without exception, and all roadways shall be carefully examined immediately before each shift by a competent person, who shall be known as the fire boss, appointed by the superintendent and mine foreman for that purpose. The person or persons making such examination shall use no light other than that enclosed in a safety lamp while making such examination. In all cases, said examination shall be begun within the shortest possible period of time necessary to complete such inspection before the regular time appointed to commence work, but in no case shall said examination be begun more than three (3) hours prior to the appointed time of each shift in commencing work, and it shall be the duty of the said fire boss to examine for all dangers likely to be found, and after each examination to leave at the face and sides of every place so examined, evidence of his presence, and he shall at each examination, inspect the entrance, or entrances, to the worked out or abandoned parts, which are adjacent to the roadways and working places of the mines where fire damp is likely to accumulate, and in every working place and all other places where explosive gas is discovered, also where immediate danger is found to exist from other causes he shall place a danger signal across the entrance to such places, which shall be a sufficient warning for all persons not to enter said place.