2006 New York Code - Fire Tower.

 
    §  27-376.1  Fire  tower.  Fire towers may be used as exits in lieu of
  interior stairs provided they comply with all of  the  requirements  for
  interior stairs, except as modified below.
    (a)  The  enclosing  walls  of  fire  towers shall be of incombustible
  materials or assemblies having a fire-resistance rating of at least four
  hours. Such walls shall be without openings, except for doors serving as
  means of egress.
    (b) At each story served by a fire tower, access to the  stairways  of
  such fire tower shall be provided through outside balconies or fireproof
  vestibules.  Such  balconies  or vestibules shall be at least three feet
  eight inches in width and shall have unpierced floors  of  incombustible
  materials and shall be provided with substantial guard railings at least
  four feet high, without any openings greater than five inches in width.
    (c)  Such  balconies  or vestibules of fire towers shall be level with
  the floors of the structure and the platforms of the stairs connected by
  such balconies. Such balconies or vestibules shall be separated from the
  structure and the stairs by self-closing swinging doors with a  one  and
  one-half  hour fire protection rating, capable of being opened from both
  sides without the use of a key or other unlocking device.
    (d) Balconies or vestibules of fire towers shall open on a  street  or
  yard,  or  on  a  court  open vertically to the sky for its full height,
  having a minimum net area of one hundred five square feet and a  minimum
  dimension  of  seven feet. The opening from the vestibule to the street,
  yard or court shall have a minimum area of eighteen square  feet  and  a
  minimum  dimension of two feet six inches. It shall be unlawful to leave
  openings in the court walls surrounding an interior  fire  tower,  other
  than  the  openings  from  the  vestibules,  within  fifteen feet of the
  balcony, except that self-closing windows with a three-quarter hour fire
  protection rating may be used if such windows are at least ten feet from
  the balcony, provided that the area of the court is at least twelve feet
  by twenty-four feet.
    (e) Fire towers shall terminate at grade level and shall exit directly
  to the street independently of corridors serving other stairways, except
  when the fire tower terminates in the ground floor corridor  outside  of
  the inner vestibule and within ten feet of the building line.
    (f)  Fire  tower  stairs  shall  comply in all other respects with the
  applicable requirements of section 27-375 of this code.