2006 New York Code - Windows And Skylights For Public Halls And Stairs.

    §  108. Windows and skylights for public halls and stairs. 1.  Where a
  window or windows are required to light a public hall or  part  thereof,
  at  least one of such windows shall be not less than two feet six inches
  wide and five feet high. Every required window in such a hall shall open
  upon a street, yard or court. On the top story  of  such  a  dwelling  a
  ventilating skylight of the same dimensions shall be accepted in lieu of
  a window for that story.
    2.  There  shall be in the roof, directly over each required stair and
  fire-stair a ventilating skylight provided with louvres  or  ventilators
  having  a  minimum  open  area of forty square inches. The roof of every
  such skylight shall  be  glazed  with  plain  glass  and  equipped  with
  suitable  metal  screens  above and below. The glazed area of every such
  skylight shall be at least twenty square feet, except  that  in  such  a
  dwelling  or  section  thereof  two stories or less in height the glazed
  area of such a skylight need be only nine square  feet.  In  lieu  of  a
  skylight, a window of the same area as prescribed in subdivision one may
  be  provided.  If  such  a  window  is used in lieu of a skylight, fixed
  louvres having a minimum opening of forty square inches  shall  also  be
  installed in or directly adjacent to such window.
    3.  When  any  stair,  fire-stair  or  fire-tower  in  such a dwelling
  terminates at the level of a setback of an outer wall and  such  setback
  consists  of a terrace at least four feet in width, measured between the
  inside of the parapet wall and the wall of the dwelling and at least ten
  feet in length, measured parallel to the wall of the dwelling, there may
  be provided in lieu of such skylight a fireproof door and assembly  with
  the  door  self-closing  giving  access from such stair or fire-stair to
  such terrace. Such door shall have a panel at least five square feet  in
  area  glazed with wire glass and shall be equipped with louvres having a
  minimum open area of forty square inches.

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