Section 51. Shafts, elevators and dumbwaiters

1. Every shaft constructed
  after April eighteenth, nineteen hundred twenty-nine,  in  any  multiple
  dwelling  shall  be enclosed on all sides with fireproof walls and shall
  have fireproof doors and assemblies at  all  openings,  with  the  doors
  self-closing.  Dumbwaiter  shafts,  except those adjoining public halls,
  may be constructed with walls of gypsum plaster blocks approved  by  the
  department, at least two inches thick if solid and at least three inches
  thick if hollow.
    2.  All dumbwaiter doors constructed after such date shall be fastened
  by an interior lock in the shaft operated and controlled from a  central
  point in the cellar or lowest story if there be no cellar.
    3. The doors of every elevator shaft constructed after such date shall
  be  provided  with  an  automatic  device  approved by the department 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 may have a vision
  panel of wire glass not exceeding one square foot in area.
    4. Every elevator installed after such date shall be equipped  with  a
  gate  with an automatic device approved by the department to prevent the
  normal operation of such elevator unless such gate is closed.
    5. When any elevator or dumbwaiter constructed after such  date  opens
  into more than one stair, elevator vestibule or other public hall on any
  floor,  such elevator or dumbwaiter shall be placed in a separate shaft.
  Not more than three elevators or two dumbwaiters shall ever be placed in
  the same shaft.
    6. Every dwelling erected after such date which exceeds six stories or
  sixty feet in height shall  be  equipped  with  one  or  more  passenger
  elevators,  operative  at  all  times,  at  least  one of which shall be
  accessible to every apartment above the entrance story.
    7.  In  every  multiple  dwelling,  elevator  shafts,  not  previously
  enclosed  to  the satisfaction of the department, shall be enclosed with
  fireproof walls and shall have fireproof doors and assemblies, with  the
  doors self-closing.