Section 27-761. Corridors

Unless  natural  sources complying with section
  27-749 of article six of this subchapter provides  ventilating  openings
  equivalent  to  at  least  two  and  one-half percent of the floor area,
  corridors in buildings of occupancy groups H-1, J-1 and  J-2  more  than
  three  stories  in  height, shall be mechanically ventilated by a system
  supplying at least one-half cubic foot of outdoor  air  per  minute  per
  square  foot of floor area. When air conditioned, a part of the required
  supply may be recirculated as  equivalent  outdoor  air,  but  at  least
  thirty-three  and  one-third percent of the required air supply shall be
  actual outdoor air.