Section 131. Shafts, elevators and dumbwaiters

Every  shaft  shall be
  enclosed on all sides with fireproof  walls  and  shall  have  fireproof
  doors  and  assemblies at all openings, with the doors self-closing. Not
  more than three elevators or dumbwaiters shall ever  be  placed  in  the
  same  shaft.  All dumbwaiter doors shall be fastened by an interior lock
  in the shaft operated and controlled from a central point. The doors  of
  every  elevator  shaft  shall  be  provided  with an automatic device to
  prevent the normal operation of the elevator unless the hoistway door at
  which the car is standing is closed and locked, or unless  all  hoistway
  doors   are  locked  in  a  closed  position.  Such  doors,  except  for
  power-operated sliding doors, shall have a vision panel  of  wire  glass
  not  exceeding one square foot in area. Every elevator shall be equipped
  with a gate or door with an  automatic  device  to  prevent  the  normal
  operation of such elevator unless such gate or door is closed.