Section 149. Public halls

1. Every public hall shall be everywhere at least
  three feet in clear width.
    2.  Every  public  hall  shall  be  completely enclosed with fireproof
  floor, ceiling and walls, and, in dwellings erected under plans filed in
  the department after September first, nineteen hundred  fifty-one,  such
  hall  shall  be  separated  from  every stair by fireproof partitions or
  walls. All doors and their assemblies opening from such hall  or  stairs
  shall  be  fireproof,  with the doors self-closing and without transoms,
  except that in a dwelling three stories or less in  height  occupied  by
  not  more  than four families on each story, or in a class A dwelling or
  any section thereof two stories or less in height, any such  hall  which
  furnishes access to only one stair need not be separated from such stair
  by  any  partition  or  door  and  the  walls  of  a  public hall may be
  fire-retarded and the floors may be provided with three inches  or  more
  of  incombustible deafening materials between the beams instead of being
  fireproof.
    3. Except in dwellings three stories or less in height and occupied by
  two families  or  less  on  every  story,  and  except  as  provided  in
  subdivisions  four  to  seven inclusive, every public hall shall have at
  least one window opening directly upon a street or upon a lawful yard or
  court. There shall be such a window at the end of each such hall and  at
  right angles to its length, with an additional window in each forty feet
  of  hall  or  fraction thereof beyond the first sixty feet from such end
  window; or the hall shall have one window opening directly upon a street
  or upon a lawful yard or court in every forty  feet  of  its  length  or
  fraction thereof measured from one end of the hall.
    4.  When the length of any recess or return off a public hall does not
  exceed twice the width of such recess or  return,  no  window  shall  be
  required  therein. But whenever the length of a recess or return exceeds
  twice its width, there shall be an additional window or windows  meeting
  the requirements for a separate public hall. No entrance hall shall have
  a return or recess which exceeds in length twice its width.
    5.  The  foregoing  provisions of this section with regard to lighting
  and ventilation shall not apply to a  vestibule  or  other  public  hall
  which  serves  as  a means of access from one or more apartments opening
  thereon to a  fire-stair  or  fire-tower  meeting  the  requirements  of
  section  one  hundred  forty-four  if  such  vestibule or public hall is
  lighted and ventilated as required for fireproof dwellings  by  sections
  thirty-seven and one hundred seven.
    6.  The  foregoing  provisions of this section with regard to lighting
  and ventilation shall not apply to that  portion  of  an  entrance  hall
  between  the  first  flight  of  stairs  and  the  entrance provided the
  entrance door contains five square feet or more  of  glazed  surface  or
  such  entrance  hall  does  not  extend  from  the outer entrance of the
  dwelling more than sixty feet.
    7. A passenger elevator vestibule not exceeding in  length  twice  the
  parallel length of the elevator shaft or shafts opening into it need not
  be equipped with a window if it conforms to the requirements of sections
  thirty-seven  and  one  hundred  seven  for  public  halls  in fireproof
  multiple dwellings. Every  door  and  its  assembly  separating  such  a
  vestibule  from  any  public  hall connected with a stair, fire-stair or
  fire-tower shall be fireproof, with the  door  self-closing  and  glazed
  with  good  quality  wire glass ten square feet or more in area. No such
  door shall be kept open by any device whatever.
    8. Any part of a public hall that is shut off from any other  part  of
  such hall by a door or doors shall be deemed a separate hall.