34 Pa. Code § 50.32
Shafts less than 9 square feet in area not complying with § 50.31 (relating to vertical openings 9 square feet or more) shall have enclosing walls or be lined with sheet metal having lock jointed or riveted seams and joints. Combustible material, partitions, and floors through which shafts pass shall be kept at least 3 inches from the metal lining or shall be protected by the equivalent of 3/8 inch of plaster or plaster board. Openings between shafts and the floor construction through which they pass shall be filled with noncombustible material, securely held in place to prevent the passage of fire. Doors opening into the vertical shafts shall be of metal or shall be covered on the shaft side by the equivalent of 1/4 inch of asbestos and not less than 26 gauge steel turned around all edges and securely fastened to the door.
34 Pa. Code § 50.32
This section cited in 34 Pa. Code § 51.31 (relating to vertical openings); 34 Pa. Code § 52.31 (relating to vertical openings); 34 Pa. Code § 53.31 (relating to vertical openings); 34 Pa. Code § 54.31 (relating to vertical openings); 34 Pa. Code § 55.31 (relating to vertical openings); 34 Pa. Code § 57.31 (relating to vertical openings); 34 Pa. Code § 58.31 (relating to vertical openings); and 34 Pa. Code § 59.31 (relating to vertical openings).