Noncombustible Buildings— Death Traps for Fire Fighters
departments
The Volunteers Corner
When used to designate a type of building construction, the term “noncombustible” becomes an illusion of safety that conceals the inherent danger to fire fighters that is associated with this type of construction.
Two things must be kept in mind when responding to a fire in a noncombustible building:
- The building itself will not burn, but it is likely to collapse during an interior fire.
- Although the structural components of the building will not burn, the contents will usually burn.
When a working fire occurs in a noncombustible building, you must expect sections—or all—of the building to collapse. When faced with this danger, fire fighters must get out of the building before collapse becomes imminent.
Construction: Common to noncombustible buildings is an unprotected steel frame. The roof may be supported by arched steel trusses or flat steel trusses, more commonly known as bar-joists. In some noncombustible buildings, the roof rests on steel I-beam rafters and steel purlins (the I-beams connecting the rafters to provide attachment for the roof deck).
The walls can be made of flat steel sheets—often corrugated steel in older buildings—corrugated asbestos cement board or concrete blocks. Except when the wall is made of cement blocks, the columns are always steel. Concrete block walls may or may not have steel columns.
Obviously, the all-steel walls or those with asbestos cement board on steel framing will collapse independently of roof collapse when fire heats the steel sufficiently. Roof failure alone also may cause walls to collapse. When the building has unprotected steel trusses— either arched or bar-joists—expansion or twisting of the trusses can cause collapse of concrete block walls. It is important to remember that a great difference in temperature between the fire-heated interior side of a concrete block wall and the outside of the wall can cause the wall to crack, bulge and fail.
Initial attack: With these facts in mind, the first-in company officer at a serious fire in a noncombustible building must make some critical decisions during his initial size-up. He has to estimate the effect of the fire on the stability of the building in terms of heat being produced by the fire and the length of time it has been burning at high intensity. In some cases, he may estimate that the building will maintain its integrity for as long as 10 or 15 minutes. In other cases, the indications may be that the building is within five minutes or less of partial or total collapse.
A safe rule is that a fully involved noncombustible building is about to collapse. Keep in mind that you did not build this death trap and your first responsibility in such a situation is to protect the lives of your fire fighters. They cannot, be replaced, but the building can.
The first-in officer also must realize that a working fire in a noncombustible building must be extinguished as rapidly as possible. We are not discussing the fire that can be quickly darkened down with a 1 ½-inch line. We are considering a fire of sufficient volume to provide a challenge.
The officer must react to that challenge by putting into operation a stream that is large enough to reduce the volume of fire. While a 2’/2-inch line—or a 1¾-inch line with an automatic nozzle—may be adequate for some fires, the use of master stream equipment may be the first best move to take at other larger fires. Water damage is of no consideration when the immediate possibility is collapse of the building.
Looking ahead: Noncombustible buildings are becoming more popular for industrial, warehouse and even office occupancies. Before more are built in your community, you should endeavor to get the odds more on your side by fighting for changes in building codes.
If noncombustible buildings were fully sprinklered—including office areas that sometimes are built inside industrial and warehouse occupancies—your chances of being able to extinguish a fire without collapse of the building would be greatly increased. Require a fire detection system that transmits an alarm to your dispatch center and you will further improve the odds.
As in any other building seriously involved in fire, roof ventilation is a prime need in a noncombustible building. The problem is that the time between flashover and structural collapse is so short in noncombustible buildings that the roof can already be unsafe by the time the first companies arrive.
Although the roof cannot be vented by putting men on the roof, it can be vented if your building code requires plastic skylights or automatic vents on the roof. Fire heat will quickly melt out the plastic in the skylights or cause the automatic vents to open.
Curtain boards, or draft curtains, act to confine the early hot gases within a limited area under the roof. By preventing mushrooming of the hot gases, heat buildup is concentrated within the curtain board area with the result that automatic devices depending on heat for activation—sprinklers, roof vents, plastic skylights—operate earlier in the fire. Earlier operation of these devices slows fire spread and aids extinguishment.
To get these built-in fire protection aids in the next noncombustible building that will be erected in your community, you have to speak now and tell the code officials, building owner and prospective occupant the facts about noncombustible buildings.
