§ 411. Ingress and egress. The commissioner shall require that a mine
operating through either a vertical or inclined shaft, or a horizontal
tunnel, shall have not less than two adequate and accessible outlets, at
least one hundred and fifty feet apart, as a condition precedent to
employment of any person in the mine. The subterranean workings shall
connect such outlets with each other. They shall at all times provide
safe and separate passage between the subterranean workings and the
surface.