THE MORE SUBTLE FIREGROUND SURPRISES
BY TOM BRENNAN
We have been speaking of surprises on the fireground–specifically, collapse of structures after the fire service has been operating. There are too many reports of firefighter deaths and injuries attributable to “Suddenly and without warning, the structure (fully or partially) collapsed, trapping firefighters within.”
As fire service professionals, we should strive during our career to drive the element of surprise on the fireground out of existence. Collapse should be one of the easiest areas in which to do this because there are so many warning signs–the building is telling you that it probably will or definitely will collapse. Risk assessment or analysis–a term we constantly see in articles and texts lately–should dramatically increase the safety levels for our firefighters based on the ongoing size-up of conditions and the “Commandments of Firefighting.” A building devoid of inhabitants other than firefighters that shows enough indicators to forecast imminent or probable collapse must be evacuated of the additional life hazard–the firefighters–and declared to be a piece of junk. The strategy and tactics employed should be assigned and monitored as they would be for a pile of rubbish or dumpster fire.
Last month we discussed indicators that would force a “mayday” situation, causing all forces to get out any way possible–those that are easy to recognize. Other indicators are more subtle and may not immediately cry out “Strategy shift!” They present themselves first in preplanning (before or during response) and second after arrival and particular fire structure data are gathered from outside and then inside during the firefight. The ones we will discuss here are the most difficult to gather and recall, mostly because they do not have the importance put on them by our forces who are used to “beginning in da street, under da smoke”; they are those that must be gathered in preplan activities, those that are very unmacho and unromantic.
General construction. The following are listed in order of “probability of collapse during fire conditions,” which differs from being listed according to “ability to burn (ability to contribute fuel to the fire).”
1. Fire-resistive structures–usually framed buildings, meaning that the walls do not support the floors. They generally are constructed as a skeleton of steel, masonry columns and beams, or a combination. Walls then are “hung on the skeleton as a skin” to beautify and control the elements. Heavy sustained fire will cause concrete spalling or local collapse after some time.
2. Heavy timber or mill structures–thick masonry enclosure, bearing, and partition walls; massive wood interior supports and flooring. These structures, while able to contribute great amounts of fuel, do not readily collapse. There are exceptions, though. Collapse awareness on the fireground is of a lower priority than the rest of our structures–USUALLY.
3. Ordinary structures–masonry walls and wood interior supports and floors.
4. Frame structures–all wood–America`s residence. The thing about these structures is that fire usually begins to drive us out of the area or structure prior to collapse. This is another “experienced” truth you should never depend on. In these structures, danger for partial collapse of stairs, portions of rooms above fire, and portions of structures overhead–cockloft and attic spaces–always exists. Staircases whose undersides are exposed to fire should always be considered too weak for firefighter support and should be reinforced by portable ladder.
5. Noncombustible construction–masonry walls and lightweight metal truss (usually parallel chord) supporting preshaped (Q-decking) built-up metal roofs. The odd thing about this construction is that the construction label “noncombustible” gives a false sense of security to our forces. We should rely on other people`s experiences with such buildings and believe that if the truss assembly is exposed to fire it will fail in a short time. Being lightweight, the failing roof in commercial buildings usually is supported by shelving assemblies onto which it falls. The major life threat here is to the vertical ventilation team on the roof–for many reasons.
6. Lightweight wood truss assembly frame buildings (new collapse awareness construction category)–this construction puts a cockloft on every floor of multistory buildings. This is our worst type of construction when considering that collapse will be a major factor. If fire is within and exposed to the “lumberyard of toothpicks,” failure will occur in five to 10 minutes. You must know that this construction exists within the structure before you arrive at the fire. That means preplanning is a must! These structures are erected with lightning speed in your district, and if you don`t see the picture before it is sheathed over, you never will.
Occupancy. What is in the building and what is the building used for? Knowing this is a major benefit of preplanning. First, what was the building designed for and what is it holding up now? Occupancy change in older buildings is one of the greatest collapse causes during fire in ordinary construction. Older downtown buildings go out of business in reaction to a new shopping mall, and the “mom and pop” candy store now stores used refrigerators–it was never designed to support that load!
The second occupancy hazard lies in absorbent storage. Furniture warehouses, paper and cardboard products, and other “rag shops” hold virtually every ounce of water applied into the structure. If you have a fire flow of up to 1,000 gallons–five handlines–you are talking about four tons of weight added to the floor supports every minute of firefighting.
A subtle third occupancy hazard is high-rack storage. It causes fire to burn longer, attacking the integrity of the structure and the stacking supports. Fire location is more difficult to determine in these maze-like structures; also, once it is located, it is difficult to deliver handline streams to the seat of the fire itself. More next month.
TOM BRENNAN is chief of the Waterbury (CT) Fire Department and a technical editor of Fire Engineering. He spent more than 20 years in some of the world`s busiest ladder companies in the City of New York (NY) Fire Department.
