Section 231. Egress

1. Every non-fireproof tenement exceeding two stories
  in height and every fireproof  tenement  erected  after  May  sixteenth,
  nineteen  hundred thirteen, shall have at least two independent means of
  egress, which shall extend from the ground story to the roof, be located
  remote from each other and be separated from each other by walls.
    2. One of such means of egress shall be a flight of stairs constructed
  as  provided  in  sections  two  hundred  thirty-three  to  two  hundred
  thirty-eight  inclusive;  but  this  sentence  shall not be construed to
  require any alteration in the material or width  of  any  stair  or  its
  treads  and  risers  lawfully  permitted  on  April eighteenth, nineteen
  hundred twenty-nine.
    3. The other required means of egress shall be directly accessible  at
  each  story  to  each apartment without having to pass through the first
  means of egress. Such other means of egress shall  be  any  one  of  the
  following, as the owner may elect:
    a. A system of outside fire-escapes constructed as provided in section
  fifty-three.
    b.  An  additional  stair,  either  inside or outside, constructed and
  arranged as provided in sections two hundred thirty-three to two hundred
  thirty-eight inclusive.
    c. A fire-tower or fire-stair constructed and arranged as provided  in
  section two hundred thirty-nine.
    d.  Except as provided in subdivision nine of section fifty-three, any
  means of egress lawfully permitted on April eighteenth, nineteen hundred
  twenty-nine,  except  wire,  chain,  cable,  vertical  ladder,  or  rope
  fire-escapes.