No person shall enter such mine or mines for any purpose at the beginning of work upon shift therein until such signal or warning has been given by the fire boss or bosses as to the safety thereof, as by statute provided, except under the direction of the fire boss or bosses, and then for the purpose of assisting in making the mine safe: Provided, however, That miners regularly employed on a shift during which the mine is being preshift examined by a fire boss or certified person shall be permitted to leave or enter the mine in the performance of their duties.
West Virginia Legal Code