2006 New York Code - Public Stairs.

 
    §  257.  Public stairs. 1. Every stair and fire-stair shall, except as
  otherwise provided in subdivisions three and four of this section and in
  section  two  hundred  fifty-nine,  be  constructed  as   provided   for
  fire-stairs  in  sections  two  hundred  two  and  two  hundred five for
  fireproof dwellings.
    2. Every stair and fire-stair shall be at least three  feet  in  clear
  width  throughout,  and at all floor levels shall have landings at least
  three feet eight inches in clear width.
    3. Every stair and fire-stair shall be completely separated from every
  other stair and fire-stair and from  every  public  hall  and  shaft  by
  fireproof  walls,  with  fireproof  doors and assemblies, with the doors
  self-closing and without transoms,  at  all  openings,  except  that  in
  dwellings two stories or less in height such walls may be fire-retarded.
  The  doors  giving  access  to such stairs shall not be held open by any
  device whatever.
    4. Except in the case of an interior enclosed stair separated from and
  directly accessible to the public hall by a self-closing fireproof  door
  and  except  as provided in subdivision five, there shall be provided to
  light and ventilate every stair at  every  story  a  window  or  windows
  opening on a street, court or yard.
    5. In a dwelling occupied by two families or less on every story:
    a.  If  such dwelling is three stories or less in height, there may be
  provided for any stair, in lieu of windows, a stairwell  sixteen  inches
  or more in clear width extending from the entrance story to the roof.
    b.  If  such  dwelling  is  a permanently occupied dwelling and is two
  stories or less in height, there may be provided for any stair, in  lieu
  of  windows,  a  stairwell  six  inches  or more in clear width. For the
  purposes of this paragraph, a section of a permanently occupied dwelling
  may be deemed a separate multiple dwelling.
    c. If such dwelling is two stories in height and has no public hall on
  the first story, no stairwell or stair windows need be provided.