Section 27-342. Openings in fire divisions and separations

Openings in fire
  divisions  and  fire  separations  that   are   required   to   have   a
  fire-resistance rating, shall be protected by opening protectives having
  the  fire-resistance  ratings  prescribed in table 5-3, shall not exceed
  the limits in size and area herein prescribed, and shall comply with the
  provisions of section 27-329 of article three of this subchapter.   Door
  and  other  openings  in enclosures of vertical exits, exit passageways,
  corridors,  and  places  of  assembly  shall  be  protected  by  opening
  protectives  as  required by the provisions of subchapters six and eight
  of this chapter.  When such enclosures also serve as fire  divisions  or
  fire separations, openings therein shall be protected as required by the
  provisions of this subchapter.
    (a)  Size of opening. In buildings that are not sprinklered no opening
  through a fire division or fire  separation  shall  exceed  one  hundred
  twenty  square feet in area, with no dimension greater than twelve feet,
  and the aggregate width of all openings at any level  shall  not  exceed
  twenty-five  percent of the length of the wall.  Where the areas on both
  sides  of  a  fire  division  or  fire  separation  are  sprinklered  in
  accordance  with  the construction provisions of subchapter seventeen of
  this chapter, the size of the opening may be one  hundred  fifty  square
  feet in area, with no dimension greater than fifteen feet.  In buildings
  fully  sprinklered  in  compliance  with  the  provisions  of subchapter
  seventeen of ths chapter, the  size  and  aggregate  width  of  openings
  through  fire  divisions or fire separations shall be unlimited.  When a
  fire division or fire separation serves as a horizontal  exit  also,  it
  shall  have  no opening other than door openings not exceeding fifty-six
  square feet in area, the aggregate width of all openings  at  any  level
  shall  not  exceed  twenty-five  percent  of the length of the wall, and
  shall comply with the provisions of section 27-373 of  article  five  of
  subchapter six of this chapter.
    (b)  Conveyor  openings.  Where fire doors or shutters are impractical
  for the protection of  conveyor  openings  in  fire  divisions  or  fire
  separations, a system of water spray nozzles may be used.  At least four
  nozzles  shall  be  provided  on  each side of the opening so as to give
  complete coverage of the opening.   Nozzles shall be  controlled  by  an
  automatic  valve  actuated by a heat detector.  Nozzles shall be located
  at an angle not more than  thirty  degrees  between  the  centerline  of
  nozzle  discharge  and a line perpendicular to the plane of the opening.
  The water discharge rate shall be at least three gallons per square foot
  per minute.  When conveyor openings through floors are protected by this
  method, the openings shall also  be  provided  with    a  noncombustible
  enclosure  constructed  around  the  conveyor  from  the  floor up to or
  slightly beyond the spray nozzles, and draft curtains shall be  provided
  extending twenty-four inches below and around the floor opening.
 
                                  Table 5-3
         Opening Protectives for Fire Divisions and Fire Separations
 
       Fire-Resistance Rating of Fire     Fire Protection Rating
       Division or Fire Separation        of Opening Protective
       in which Opening Occurs (hr.)
 
          3 or 4                            3 hr. (Class A)*
          2 or 1-1/2                        1-1/2 hr. (Class B)
          1                                 3/4 hr. (Class C)

    * Note--Shall  consist  of two one and one-half hour (class B) opening
  protectives, with one protective  installed  on  each  face  of  a  fire
  division or fire separation.