Section 217. Lighting and ventilation of public halls and stairs

1.  In
  every tenement erected after April twelfth, nineteen hundred one,  which
  exceeds  four stories in height or is occupied by three families or more
  on any story, every public hall shall have at least one  window  opening
  directly  upon  a street, yard or court. Such window shall be located at
  the end of the  hall  and  at  right  angles  to  its  length,  with  an
  additional window in each thirty feet of hall or fraction thereof beyond
  the  first  sixty  feet from such end window if the tenement was erected
  after April eighteenth, nineteen hundred twelve; or, if  the  window  is
  not  thus  located  at  the end of the hall, there shall be at least one
  window opening directly upon a street, yard or  court  in  every  twenty
  feet  of  the  length of the hall or fraction thereof, measured from one
  end of hall; but the  foregoing  provisions  shall  not  apply  to  that
  portion of an entrance hall between the entrance and the first flight of
  stairs  if the entrance door contains five square feet or more of glazed
  surface.
    2. When the length of any recess or return off of  a  public  hall  in
  such  a  tenement  does  not  exceed twice its width, no window shall be
  required therein. But wherever the length of a recess or return  exceeds
  twice  its  width there shall be an additional window or windows meeting
  the requirements for a separate public hall.
    3. Except as provided in subdivision four, a  tenement  erected  after
  April  twelfth,  nineteen  hundred one, which is four stories or less in
  height and occupied by not more than two families  on  any  story  shall
  either have windows in its public halls as above provided or a stairwell
  twelve  inches or more in width extending from the entrance story to the
  roof. In such a tenement, except as provided in subdivision four,  every
  entrance  door shall contain five square feet or more of glazed surface,
  and all doors leading from the  public  halls  shall  be  provided  with
  translucent  glass panels five square feet or more in area for each door
  and fixed transoms of translucent glass over each door.
    4. Neither such windows nor such a  stairwell  shall  be  required  in
  cities  of  one  million  or  more  population in tenements which do not
  exceed three stories in height or fifty-five feet in depth and which are
  occupied by not more than one family on  any  story  and  in  which  the
  stairs  descend  in  a straight and continuous run from the top story to
  the entrance story with proper landings at each  story.  Such  tenements
  shall  not  be  required  to  have glass panels or transoms in the doors
  leading from the public halls.
    5. In every public hall that is provided with a window or windows in a
  tenement erected after April twelfth, nineteen hundred one, at least one
  such window shall be at least two feet six inches  wide  and  five  feet
  high.
    6.  In  every  such  tenement  there shall be provided, at every floor
  level, a window opening upon a street, yard,  court  or  space  above  a
  setback  to  light and ventilate every stair. Every such required window
  shall be of the size required by subdivision five, except that a  window
  opening  upon  a  street need be only four feet high. On the top story a
  ventilating skylight of the same dimensions shall be accepted in lieu of
  a window for that story.
    7. In every such tenement there shall be in the  roof,  directly  over
  each  stairwell,  a ventilating skylight provided with ridge ventilators
  having an opening of at least forty  square  inches,  or  provided  with
  fixed  or movable louvres. The roof of every such skylight shall have at
  least twenty square feet of glazed surface. If  the  stairs  and  public
  halls  are  not  provided at each story with windows opening directly to
  the outer air, the skylights shall be provided  with  ridge  ventilators
  and also with fixed or movable louvres or movable sashes.

    8.  A  sash  door  shall  be deemed the equivalent of a window for the
  purposes of this section if it contains the  amount  of  glazed  surface
  prescribed for such windows.
    9.  In  all  old-law  tenements  the  public halls and stairs shall be
  provided with such skylights, ventilators, windows in bulkheads or other
  means of lighting and ventilation as may be deemed  practicable  by  the
  department.
    10.   All   skylights  installed  in  old-law  tenements  after  April
  eighteenth, nineteen hundred twenty-nine, shall be provided  with  ridge
  ventilators  having  an opening of at least forty square inches and also
  with fixed or movable louvres or with movable sashes. They shall  be  of
  such  size as may be determined to be practicable by the department, and
  the roofs of such skylights shall be glazed with  plain  glass  equipped
  with suitable wire screen above and below.
    11.  Whenever  a  public  hall in any old-law tenement four stories or
  more in height is not light enough in the daytime to permit a person  to
  read  in  every  part thereof without the aid of artificial light, every
  door at the end of such hall or opening therefrom into a room shall have
  a wire glass panel or panels of an  aggregate  area  of  at  least  four
  square  feet; or in lieu thereof such hall may be lighted by a window or
  windows opening upon a street or upon a lawful  yard,  court  or  shaft,
  with  the plane of each such window at right angles to the length of the
  hall. In any such tenement  any  public  hall  or  stair  which  is  not
  provided  with a window opening directly upon a street or yard and which
  is not sufficiently lighted in the opinion of the  department  shall  be
  provided by the owner with artificial light, which shall be kept burning
  at all times.
    12.  Any part of a public hall that is shut off from any other part of
  such hall by a door or doors shall be deemed a  separate  hall  for  the
  purposes of this section.