All-Metal Buildings House Collapse Threat in Fires
DEPARTMENTS
The Volunteers Corner
They are sometimes described as “fireproof” buildings because they won’t burn. However, when their contents are seriously involved in fire, these buildings will collapse within a brief time.
We are referring to the all-metal, modular buildings that are proliferating in all types of areas-urban, suburban and rural. These buildings have a steel frame and steel sides. The roof decks also are usually steel.
This type of construction is one story high, but in some buildings, the one story equals one and a half or two stories in height. These buildings are used as warehouses, automotive repair shops, garages, school additions, office facilities and almost anything else that can be conveniently and economically housed by this type of construction.
Fire problem: Although it is tempting to point to the use of these buildings as warehouses for combustible materials-or even noncombustible articles packed in corrugated cardboard cartons-as the prime example of contents that can rapidly cause collapse of the building, that can be misleading. Of course, if that kind of storage starts burning, the all-metal building is headed for rapid collapse.
The point to remember is that the amount of combustibles does not have to be large for these buildings to collapse in a fire. Grade school classrooms are not regarded as having a severe fire load, but they have enough combustibles in them to collapse steel Ibeams and H-columns.
As the steel frame starts falling, it will bring steel farther from the main body of heat down with it. As the roof and walls fall, they will shield the burning contents from the reach of hose streams. Thus, the fire attack becomes increasingly difficult. That is, it becomes increasingly difficult until the combustible contents of the building have burned themselves out. That is about what happened at the K mart warehouse fire, which is the subject of an article in this issue of Fire Engineering.
The fire attack: With all these cards stacked against him, the first-alarm chief must make bold decisions. He must make a size-up that will result in one of two decisions: A. The fire can be extinguished with one hand line. B. The fire cannot be extinguished with one hand line.
If one hand line can extinguish the fire, then the chief must see that the first line in has a large enough rate of flow to take care of the situation.
What if the fire cannot be extinguished with one line? Then the chief has to forget all the cliches he has ever learned about causing water damage. He has to have the common sense to recognize the simple truth that only when you make a good stop and save most of the building do you ever hear complaints about water damage. No one complains about water damage at a total loss.
A heavy application of water is the only technique the chief can use to save an allmetal building with a working fire. If the first-alarm response has the capability and the fire is accessible, the chief should give serious consideration to using a master stream as the first water on the fire. The objective is to darken down the fire before the heat causes the building to collapse.
Actually, what we are talking about is a blitz attack-a master stream flowing at least 500 gpm. If the capability for a larger stream is available, use it. The important thing is to use the highest possible rate of water flow. If the pipeman shuts down when the fire has been darkened down, then he will not waste water and cause excessive water damage.
More master streams may be needed, or hand lines may have to be stretched to reach fire in areas difficult to penetrate otherwise. Remember, your attack lines have to be operating before collapse occurs. Once the roof and walls start falling, they will shield much of the fire from hose streams and your efforts will be woefully ineffective.
Roof ventilation: In most buildings with a working fire, the chief immediately attempts to open up the roof. Unfortunately, that highly desirable tactic is too frequently impossible in these metal buildings with their metal roofs-and all the steel framework unprotected!
This means that if roof ventilation is ever to be accomplished, it must be done at fires small enough to raise the question of whether roof ventilation is really necessary. If you wait until it is necessary, it is too late. It just takes too long to open up a steel roof deck. The risk of putting fire fighters on the roof then becomes too great.
If you are lucky, the roof will have plastic skylights at close intervals. These are a tremendous help with ventilation because they melt away at a relatively low temperature and even more fortunate, they melt over the area with the highest heat. They do automatically what every ladder company tries to do in opening up a roof.
When flames erupt from the skylight openings, leave them alone. They are working for you. Never, never put an aerial stream into these roof openings. Getting the hot gases out of the building is a gigantic pips for a successful attack.
Above all, the first-alarm chief should be cautious about sending fire fighters into allmetal buildings. He has to judge the intensity of the fire and its effect on the structural stability of the buildings. He should remember: When in doubt keep ’em out!
