Section 27-759. Bathrooms and toilet rooms

Bathrooms and toilet rooms shall
  be ventilated as follows:
    (a) When ventilated by natural means, the natural ventilation  sources
  shall  comply  with section 27-749 of article six of this subchapter and
  shall have an unobstructed free area of at least five per  cent  of  the
  floor  area.  In  no  case  shall  the  net free area of the ventilation
  sources be less than  one  and  one-half  square  feet  except  that  in
  occupancy   groups   H-1  and  H-2,  provided  the  ventilation  opening
  conforming with section 27-749 of article six of this subchapter may  be
  in  a  vent  shaft provided that the net free area of the opening is not
  less than three square feet. The vent shaft cross-sectional  area  shall
  be increased by one-fifth of a square foot for every foot of height, but
  shall  not  be  less than nine square feet in area and open to the outer
  air at the top; or, the vent shaft may be open at the  sides  above  the
  roof,  with  louvres  providing  an equivalent net free area at the top,
  equal to the area of the shaft.
    (b) By individual vent shafts or ducts constructed  of  noncombustible
  materials  with  a  minimum  cross-sectional area of one square foot and
  one-third additional square foot for each  additional  water  closet  or
  urinal above two in number. The upper termination of such ducts shall be
  equipped with a wind-blown ventilator cap.
    (c)  When  a  bathroom  or  toilet  room  is not ventilated by natural
  ventilation as required  by  this  section,  it  shall  be  mechanically
  ventilated as follows:
    (1)  Rooms  containing  only  one  water  closet  or  urinal  shall be
  mechanically ventilated by an exhaust system capable  of  exhausting  at
  least  fifty  cubic  feet of air per minute. Means shall be provided for
  air ingress by louvres in the door, by  undercutting  the  door,  or  by
  transfer ducts, grilles, or other openings.
    (2)  Rooms  containing  more  than one water closet or urinal, and any
  auxiliary spaces such as those used in  hand  basins,  slop  sinks,  and
  locker rooms, shall be mechanically ventilated by an independent exhaust
  system capable of exhausting at least forty cubic feet of air per minute
  per  water closet or urinal. The outdoor air supply shall conform to the
  requirements of article seven of this subchapter.
    (3) Toilet exhaust systems shall be arranged to expel air directly  to
  the outdoors.