Section 27-344. Shafts

The requirements of this section shall apply to all
  shafts, except that floor openings accommodating a slide pole in a  fire
  house  and openings other than for ventilation, chimneys or gas vents in
  buildings three stories or less in height classified in occupancy  group
  J-3  shall  be  exempt  from  these  requirements,  and  except  as more
  restrictive requirements may be specified for chimneys and gas vents  in
  subchapter  fifteen  of  this chapter, stairway enclosures in subchapter
  six, duct enclosures in subchapter thirteen,  elevator,  escalator,  and
  dumbwaiter enclosures in subchapter eighteen of this chapter, and except
  as permitted in reference standard RS 5-18.
    (a)  Construction.  Shafts  shall be enclosed with materials having at
  least fire-resistance rating required by table 3-4. A shaft that  serves
  the  topmost  story of a building shall extend through the roof at least
  thirty-six inches above any combustible  roof  construction.  Where  the
  roof construction is of noncombustible materials, the shaft shall extend
  through  any  concealed  space  within  the  roof  construction  and may
  terminate at the underside of the roof deck. Pipes and ducts penetrating
  shaft construction shall comply with the requirements of section  27-343
  of this article.
    (b)  Combustible  Contents. Shafts shall be kept free of bookstacks or
  other combustible contents except for stair  construction  as  permitted
  under  subchapter  six  of  this  chapter,  duct  and  pipe coverings as
  permitted under subchapters  thirteen  and  sixteen,  and  elevator  car
  enclosures as permitted under subchapter eighteen of this chapter.
    (c)  Openings  in  shafts.  All  shaft openings below the top terminus
  shall be provided with opening  protectives  that  comply  with  section
  27-329 of this subchapter and table 5-3. In shafts that contain only one
  opening below the roof terminus, no opening protective need be provided.
  Openings  in  elevator  and dumbwaiter shafts shall comply only with the
  requirements of subchapter eighteen of this chapter. Where a  window  is
  located  in  a shaft wall that is an exterior wall and is ten stories or
  less above grade or three stories or less above  a  roof,  it  shall  be
  protected against entrance by a permanently secured grille consisting of
  5/8  in.  dia.  bars,  10 in. o. c. vertically, or by a stationary metal
  sash window having 1/8 in. thick solid section steel muntins, 8  in.  o.
  c.  one way. This protection shall not be required in stair shafts where
  there is a stair landing or platform not more than three  feet  directly
  below the window sill.
    (d)  Smoke  venting of closed shafts. All closed shafts having an area
  exceeding four square feet, other than elevator  or  dumbwaiter  shafts,
  shall be provided with a smoke vent having an area of at least three and
  one-half percent of the maximum shaft area at any floor, but in no event
  less  than  one-half  square  foot.  Elevator and dumbwaiter shaft vents
  shall comply with  the  requirements  of  subchapter  eighteen  of  this
  chapter.  Smoke vents may be windows, louvers, skylights, vent ducts, or
  similar devices. Vent ducts shall be enclosed by construction having the
  same fire resistance rating as required for the  shaft  enclosure.  Such
  vent  ducts  shall  extend  vertically,  diagonally,  or horizontally as
  provided below.
    (1) Through any roof of the building provided the vent opening  is  at
  least  ten feet from any window, door, outside stairway, or interior lot
  line. This dimension may be reduced to five feet if  the  vent  duct  is
  extended up to at at least the level of the top of the window or door. A
  vent that is required to extend above a roof shall extend at least eight
  inches  above  a  roof assembly constructed of noncombustible materials,
  and at least thirty-six inches above  a  roof  assembly  constructed  of
  combustible materials that are within a horizontal distance of ten feet.

    (2)  Through  an  exterior wall of the building, provided there are no
  openings in the wall within a distance of thirty feet  vertically  above
  the  vent opening, and within five feet either side of the vent opening.
  When a side of a shaft is an exterior wall or a wall of a roof bulkhead,
  the  required  vent  may  be  a  louver  or window. Any window or louver
  located in  a  shaft  wall  above  a  roof  constructed  of  combustible
  materials shall have its sill at least thirty-six inches above the roof.
    (e)  Terminus  of  shaft  vents.  Of  the total required vent area for
  shafts, at least one-third shall  be  clear  opening  to  the  outdoors,
  either  in  the  form  of  fixed  louvers,  ridge  vents,  or  hooded or
  goosenecked openings.  In lieu thereof, skylights or trap doors  may  be
  used  if  constructed and arranged to open automatically by fusible link
  or other mechanical device  when  subjected  to  a  temperature  of  one
  hundred  sixty degrees Fahrenheit or to a rapid rise in temperature at a
  rate of fifteen to twenty degrees Fahrenheit per minute.  The  remaining
  portion  of  the  required  vent area may be a window or skylight glazed
  with plain glass not more than one-eighth inch  thick  or  slow  burning
  plastic.
    (f)   Machine   rooms.   Any  compartment  containing  machinery  that
  communicates with a shaft enclosure shall comply with  all  requirements
  for  shafts.  The required louver or glazing shall not be located in any
  door leading into such compartment.