Section 258. Public halls

1. Every public hall shall be everywhere at least
  three feet in clear width.
    2.  Except  as  herein provided, every public hall shall be completely
  enclosed with fireproof floor, ceiling and  walls,  and  separated  from
  every  stair  by  fireproof partitions or walls, and all doors and their
  assemblies  opening  therefrom  shall  be  fireproof,  with  the   doors
  self-closing  and  without transoms. In a dwelling three stories or less
  in height occupied by not more than four families on each story, or in a
  permanently occupied 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 materials between the beams.
    3. Except in dwellings three stories or less in height and occupied by
  two  families  or  less  on every story, 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 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, yard or court, in every forty feet of the length of such hall or
  fraction thereof measured from one end of the hall. 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.
    4. 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 meeting the requirements of section two hundred
  two if such vestibule or  public  hall  is  lighted  and  ventilated  as
  required by sections one hundred nine and two hundred seven.