All door openings in stair and elevator enclosures shall be protected by fire doors mounted with wrought iron or steel hardware and shall be securely attached to the wall or partition or to substantial incombustible frames anchored thereto. If glass panels be used in such doors, they shall be of wired glass not exceeding seven hundred and twenty square inches in area. Interior shaft windows shall not be permitted. Doors opening into stairway shafts shall swing in the direction of exit travel, shall be self-closing and shall be at least thirty-six inches wide.

If in the opinion of the inspector or other designated official it is necessary to preserve an open elevator or hoistway in a building in existence on February 20 1917, the floor opening through which it passes shall be equipped with automatically closing trap doors not less than one and one-half inches thick, made of two thicknesses of matched boards, covered on the under side with tin. Such trap doors, when closed, shall extend beyond the openings on all sides. Such trap doors shall be protected by a substantial guard or gate, which shall be kept closed at all times except when in actual use.