§ 33.128. Doors.

 Doors used in ventilation shall be so hung and adjusted that they will close automatically. If necessary, the owner, operator or superintendent of the mine shall provide attendants for main doors whose constant duty it shall be to open them for transportation and travel and to prevent them from standing open longer than is necessary for persons or cars to pass through. A self-acting door of a type approved by the Department may be installed in lieu of maintaining a door attendant at any particular point. The framework of all doors shall be substantially secured in stone, brick, tile or concrete. The stone, brick or tile shall be laid in cement mortar unless otherwise permitted in writing by the Department or its duly authorized representative.