52 Pa. Stat. § 70-701
It shall not be lawful for the operator or superintendent of any mine to employ any person or persons in such mine or permit any person or persons to be in such mine for the purpose of working therein, unless there are in connection with every seam or stratum of coal, and from every lift thereof, worked in such mine, not less than two openings or outlets, separated by a stratum of not less than sixty feet in breadth underground, and one hundred fifty feet in breadth at the surface, at which openings or outlets safe and distinct means of ingress and egress are at all times available for the person or persons employed in the said mine. All means of ingress and egress shall be marked in a uniform manner, as prescribed by the Department of Mines and Mineral Industries, and each miner, as part of his certification requirements, shall have a thorough knowledge of the manner in which means of ingress and egress are marked. It shall be the duty of the mine foreman or assistant mine foreman to notify all of the persons working within the mine of the two nearest openings.
52 P.S. § 70-701