Section 234. Stairs and public halls

1. In every tenement erected after
  April eighteenth, nineteen hundred twelve, all stairs shall extend  from
  the  entrance story to the roof, except as otherwise provided in section
  two hundred thirty-three, and the stairs and public halls shall each  be
  at  least  three feet in clear width. Every apartment in such a tenement
  shall be directly accessible at each story to  such  stairs  and  public
  halls,  and every story of such apartment shall be so accessible to such
  a stair and public hall or  to  a  tower  fire-escape  or  stairway,  as
  provided  in  this  section  and sections two hundred thirty-five to two
  hundred thirty-nine inclusive.
    2. In every tenement erected after  April  twelfth,  nineteen  hundred
  one, except as provided in paragraph b of subdivision two of section two
  hundred  thirty-eight,  all  stairs and public halls shall be completely
  separated from all other stairs and from every elevator by  brick  walls
  or  partitions  of  terra  cotta  blocks  at least four inches thick, or
  hollow cement blocks at least four inches thick which have  successfully
  withstood  a  three-hour  standard  fire  test  and been approved by the
  department and have  fireproof  doors  and  assemblies  with  the  doors
  self-closing  at all openings. From any portion of a public hall in such
  a tenement there may be a recess which shall not be deemed a public hall
  if the walls, floor and ceilings enclosing it are fire-retarded and such
  recess is at all times adequately lighted by electric lights of at least
  fifteen watts or equivalent illumination. Such a  recess  shall  not  be
  more  than  twenty  feet long and shall not be used as a means of egress
  from more than three apartments.