HIGH-RISE CURTAIN WALL ADDS TO FIREFIGHTING CHALENGES
“Second alarm on Box 1212, 18th and Market streets. Fire is reported at 1812 Market Street on the 19th floor.”
Ladder 6 responds on the second alarm and is ordered to check the 20th floor for vertical fire spread. Battalion 5 informs the captain of Ladder 6 that Engine 27 also has been assigned to report with the high-rise hose bag to floor 20. The captain of Ladder 6 and his firelighters use the low-rise elevator bank and proceed to the 14th floor, which is the top floor of the bank. They then proceed to the 20th floor via the stairwell on the east side of the floor. Fire crews have initiated an attack on the 19th floor from the stairwell on the west side of the core.
On opening the stairwell door on the 20th floor, the captain observes a verylight smoke condition on the floor. He also observes a glow about 50 feet from the stairwell door, in one of the perimeter offices on the south side of the floor. The captain remembers observing, on entering the building, the largest volume of fire on the 19th floor, on the south side of the building, directly below the point where he observed the glow on floor 20. He immediately notifies the sector chief of his findings and instructs Engine 27 to stretch a hoseline to the 20th floor. Engine 27 stretches a hoseline toward the perimeter office while Ladder 6 removes numerous ceiling tiles to check lor a fire condition in tile ceiling plenum. There is a very light smoke condition but no fire in the plenum.
(Photos by author.)
As Engine 27 approaches the glow, the members can see through a glass floor-toceiling partition wall and observe a small amount of fire at the floor level of a wellappointed office. Hie office is on the outside perimeter of the floor, and the windows in the fire area are intact. The members of Ladder 6 force the door, and Engine 27 is able to effectively extinguish a small fire at the floor level of the office.
How was the fire able to vertically move from the 19th to the 20th floor? It spread through the gap between the floor slab and flic curtain wall.
CURTAIN WALL CONSTRUCTION
With the birth of the modern high-rise building (post-1950 construction) came prefabricated curtain wall construction Prior to this period, high-rise structures were constructed completely at the building site Steel framing was erected, concrete for flooring was mixed on location, and exterior walls were laid by brick masons on location. In modern high-rise construction, mixed concrete is brought to the site by trucks, pumped up to floors, and poured over metal Q-decking and reinforcing rods (a substantially less amount of concrete than in years past). Also of major significance are the prefabricated curtain wall panels, which are constructed off-site and shipped complete to the building site.
Around the perimeter of the floor slab, metal clip angles designed to hold the curtain wall in place are attached to the floor slab. The individual sections of curtain wall are attached to the clip angles and then also are held in place by aluminum mullions. With this type of construction, a void space is created between the floor slab and the curtain wall assembly. This void normally ranges between one inch and six inches in width and must be filled with a listed two-hour firesafing material, installed exactly as specified by the manufacturer. As with any material, its effectiveness in preventing fire spread depends to a great degree on the quality of workmanship provided during installation.
Insulation also is present behind the curtain wall panels themselves, to cut down on air movement and leakage within the building. Some firesafing manufacturers also mandate the use of a two-hour fire rated insulation for the curtain wall panel itself in addition to the firesafing in the gap between the curtain wall and the floor slab—the two protective measures work together as a “system.” In this way, the panel itself is protected from fire exposure (which, when left unprotected, could distort or break from thermal expansion caused by the fire).
Firesafing and insulation may become ineffective if rain or dampness penetrate the curtain wall and saturate the material. Also, materials removed when repairs were made may not have been replaced.
CURTAIN WALL GAP FIRE SPREAD
A lack of firesafing was a major factor in the vertical fire spread during a fire in the 62-story First Interstate Bank Building in Los Angeles in May 1988. The three-inchwide curtain wall gap had been filled with ordinary fiber insulation. Firefighters actually could see the fire spread from floor to floor via this vertical channel.
In addition to autoexposure, vertical fire spread through the curtain wall gap also was identified as a critical factor at a fire in the 38-story One Meridian Plaza in Philadelphia in February 1991. In that building, the gap between the floor slab and the exterior granite facade was approxintately 1 inches wide. Postfire inspection of tire curtain wall on the fire floors showed that, for whatever reason, no firesaftng was present in the gap.
TACTICAL CONSIDERATIONS
location. As with the use of conventional firefighting tactics, confirm the exact location of the fire. A fire condition on the peripheral area of a floor indicates the need to check for vertical fire spread through the curtain wall gap on the fhxir above the fire.
Ceiling plenum. When entering onto the llixir. remember to check the ceiling plenum area for smoke, heat, and fire conditions Specifically, remove drop-ceiling tiles and lixik into the plenum as you move toward the peripheral offices, C heck this area several times as you move toward the perimeter of the floor, since fire conditions will change.
Forcible entry. Anticipate the need for forcible entry. Is the stairwell door unlocked? Can it be unlocked remotely from the fire command center? What doors does the building’s master key unlock? How many master keys are available for firefighter use? In addition to these questions, bear in mind that the periphery of a floor usually is occupied by a firm’s prestigious offices —with prestige comes a good view, privacy, and security. Security means locked doors that require either a master key or forcible entry for access. It may be easier and cause less damage to put a hole through the drywall immediately adjacent to the dr.
Safety. Even when you are conducting routine business in a high-rise building, it is very easy to become lost on a floor due to the maze-like office configuration. Take appropriate safety measures to ensure that personnel do not become lost and that they can return safely to the stairwell, if necessary.
Communications. Communication between company officers and sector chiefs is absolutely essential during operations in a high-rise building. Specifically, sector chiefs must know the exact locations of the companies operating. Company officers should immediately inform sector chiefs of any condition that would affect the overall management of the fire.
FIRE PREVENTION CONSIDERATIONS
When conducting routine inspections, fire prevention bureau personnel should be aware of what constitutes properly installed firesafing and (possibly) fire-rated curtain wall panel insulation. Even though it is normally the responsibility of the building department inspection unit to inspect firesafing during the initial building construction, the maintenance of firesafing material is a responsibility that should not be ignored alter the building is occupied.
Iaick of or an inadequate amount of firesafing. improperly supported firesafing material (including missing clips or other support hardware), missing fire rated caulking on top of the firesafing (which many manufacturers specify must be used), and excessive gaps (greater than eight inches) between the curtain wall and slab are all causes for concern Firesafing materials are limited in the gap size they can adequately protect. Any questionable installation necessitates a review of the manufacturer’s literature and tests that have been conducted. Unfortunately, no standardized test method specific to curtain wall protection materials is in use at present
