FIRE LOSS MANAGEMENT
FIRE PROTECTION
SFPE
Part 14: MORE ON FIRE EXTENSION
A major concern in the area of fire protection is vertical extension of fire through stairways. Often stairway doors are chocked open with wooden wedges to avoid the inconvenience of having to open and close them. These wedges often are called “four-hour fusible links.” Sometimes they are necessary to balance the air conditioning system. However, from a fire protection standpoint, chocking stairway doors is an entirely unacceptable practice.
In a futile attempt to deal with this problem, many doors are provided with door checks in which fusible links are inserted. The hope is that during a fire the fusible link will fail and the door will close. As far as the spread of fire is concerned this might be satisfactory, but our overriding concern is the life hazard—the fusible link will not fail on smoke. In the totally enclosed buildings common today the spread of smoke becomes a more and more serious problem, so the fusible link method of holding doors open is also unacceptable.
Recently a superior device has been developed for keeping doors open: an electromagnetic latch. On receipt of any fire alarm—automatic or manual-buttons strategically located at suitable points cause the current through all of the electromagnetic latches to fail, and all of the doors close, preventing the spread of smoke and fire. T he doors remain serviceable for human passage.
For some designs the following test procedure is practical: When the building is closed for the evening, the guard or watchman operates one switch to close all the doors, and the first patrol discloses any inoperable ones. After the test the current is restored to the electromagnets. During night hours these doors remain closed if unused. This reduces the operational delay in the event of fire. The magnetic latch remains in the open position when first opened.
SHAFTS
Pipe shafts are a serious problem. Consider the pipe shafts in a high-rise building. Isolated from the rest of the building by fire-resistant doors at each floor, they will not assist in the spread of a fire from floor to floor, but fires can start within die pipe shafts involving pipe-covering insulation. (Asbestos pipe covering can be a double hazard—combustion and toxicity. Covering can be labeled “asbestos” if it is 51 percent asbestos; the other 49 percent may be combustible fibers.) Such fires can be difficult and costly. Because of the vertical column there is a tremendous flue effect. When an access door is opened for firefighting, a jet of fire pours out.
The potential losses as a result of a fire in a pipe shaft demand special consideration. Isolating the vertical pipe shaft from the rest of the building so that it is not a means of fire extension from floor to floor is not enough. A fire within the utility shaft can be a very severe loss—take, for example, the amount of time lost in replacing the wiring destroyed by such a fire. Consider using noncombustible insulation, fire stopping, and special automatic sprinkler protection to avoid these costly fires.
This shaft extension was noted in the 1961 Hartford (CT) Hospital fire (16 killed) involving a laundry chute. The doors to the laundry chute opened directly into the corridor rather than into a service room. The lids on the doors were aluminum. When the fire occurred, the aluminum door melted and a jet of fire poured into the corridor.
Some time ago there was a shaft fire in the Empire State Building in New York City. Many stories above the basic fire, a chief and his aide opened a shaft door. Fire roared out in such volume that it could not be knocked back, even with a 2’/2-inch hoseline. An open access door is similar to the top of a chimney and should be opened only when heavy charged lines are ready.
ACCOMMODATION STAIRWAYS
Many codes permit “accommodation stairways”—open stairs connecting two floors of a fire-resistive highrise building. These stairs can effectively double the fire area. 1’he alarm might be received from a detector on the upper of the two floors, but the fire will actually be on the lower floor. In one case a Canadian fire department followed the practice of getting off the elevator on the floor below the alarm; however, smoke from the actual fire floor traveled up the accommodation stairway and activated the alarm on the floor above—the firefighters stepped right into the fire.
POKETHROUGHS
There is potential for vertical extension when holes are opened for various reasons after the building is built. Someone in the maintenance group should be assigned the responsibility of maintaining the integrity of the building structure. He should ensure that all openings made vertically and horizontally throughout the existing building structure are sealed and maintained in a manner acceptable to fire protection codes in effect.
ELEVATOR SHAFTS
Elevator shafts and other vertical openings throughout the building should be separated from the occupied space by compartmentizing the elevator lobbies, but often they are not. In some buildings the elevator shaft is totally enclosed with standard fire doors yet is surrounded by a stairway that’s wide open from floor to floor, without fire doors.
LARGE VERTICAL OPENINGS
Sometimes protecting vertical openings with fixed physical means is undesirable. Many new suburban department stores are two and three stories high and management exerts pressure for wide-open escalators from the basement to the first floor and the first to the second floor. Although enclosures are the best means of fire protection available, these open escalators are often permitted when protected by water sprinkler systems that sometimes include automatic vents. The simple provision of closely spaced sprinklers around these openings is of dubious efficiency, however, in controlling the spread of smoke and fire gases.
This is just one example in which all the fire protection eggs essentially have been placed in the basket of a dynamic fire protection system: The sprinkler system depends not only on its static element, the piping, but on its dynamic element, the water. Yet to the best of my knowledge there is no code stipulating that if a sprinkler system (required for life safety) is turned off for any reason, the building cannot be operated as a place of public assembly.
EXTENSION FROM OUTSIDE TO INSIDE
One often-overlooked fire protection problem is the possibility of fire extension from the outside of a building to the inside. Old mills had outside sprinklers and steel shutters on all horizontal openings to protect them as an exposure to an adjacent fire building. However, people have forgotten this hazard exists. We still can find a plain glass window separating oil-filled transformers from a building housing a multimillion-dollar accelerator. The window serves absolutely no purpose. If you look out the window all you see is the transformer. Blocking up the window greatly reduces the fire loss possibility.
Specially stored flammable liquids and gases moved outside the building for safety reasons are sometimes hazardous because their new location is poorly chosen with respect to extension back into the building. Ordinary rubbish or rubbish from a construction job accumulating directly outside a building may have serious extension consequences, particularly if it is located adjacent to intakes, the ventilation system, or ordinary windows. In one case, tremendous quantities of zirconium scrap were moved an adequate distance from the building so that when the fire occurred and the thousands of pounds of scrap burned, the damage to the building consisted of a few cracked windows and scorched window frames.
Concerning outside fires, don’t neglect to appraise the loss potential of the outside wooden cooling tower, which is a feature of many scientific installations. A fire in a cooling tower sounds comical, but cooling towers actually have burned up. A wooden vessel full of water on the inside can be destroyed rapidly by a fire on the outside. If the cooling tower is essential to the operation of the facility, as many cooling systems are, it should be protected in accordance with the standards for cooling towers. The protection may cost more than the tower, but cost-conscious managers must realize that they are in fact protecting the continuity of operation, not just the tower.
Note the location of rubbish sites for truck pickups and storage areas for building material prior to their installation. Trailers containing flammable gases should be located at hard stands designed to limit fire.
One Atomic Energy Commission facility built in a major city abutted a lumberyard. The entire back wall was built without windows and provided with a water curtain. Although the plant was five stories high, the elimination of the unnecessary windows saved thousands of dollars and was an excellent fire protection design feature.
(Photos by author.)
EXTENSION FROM BUILDING TO BUILDING
Fire can extend from building to building as well as from one major section of the building to another.
The containment of a fire in the building of origin is the ultimate test of the fire service. It is really this factor that is rated by the l.S.O. when it rates the fire defenses of a city. Building construction, the water supply, the fire department, and other factors combine to limit or to enhance the possibility of extension from one building to another. Once a fire spreads from the building of origin to another building, a conflagration is underway. If the firefighting forces cannot stop the first extension, there is little hope that they can stop any further extension.
Preventing extension from building to building might involve physical protection in the form of special automatic sprinklers, the sealing up of windows, or the demolition of combustible structures between two otherwise valuable buildings. It is a common error to permit a low-value combustible building to act as a fuse train between two otherwise highly valuable buildings. To avoid extension, you must pinpoint the difficulty — inadequate water, inadequate assistance, a poorly designed building, and so on —and work to correct it.
