FACTORS THAT COULD SIGNAL A SHIFT TO DEFENSIVE STRATEGY
BY TOM BRENNAN
Last month, we left off without finishing with those pieces of information a fire department gathers during preplanning that forecast the probability of collapse and indicate a shift to defensive strategy during the firefight.
Building renovations must be detected on preplan. They present unknown dangers that have accounted for building failures resulting in firefighter deaths and serious injuries in the past. Many layers of built-up flooring and heavy materials of the first floor over a cellar fire caused the disaster in New York City that claimed the lives of 12 firefighters. The floors not only insulated the members from the fierce fire conditions below them but also provided a honeycomb of small voids through which fire spread undetected.
Similar problems are created by multiple dropped ceilings. All are hung or attached as dead load to the existing support beams for the original floor or roof above. Already overloaded support members weakened by inaccessible, undetected fire spell disaster.
Renovations in roof areas also present dangers. Known as built-up roofs or rain roofs, fire spread between the flimsy rain roof and the original roof results in rapid collapse–with no warning to those below. In addition, members on the roof cannot detect the intensity of the fire below the original roof. As a matter of fact, it masks the need to cut vertical ventilation until it is too late. A cockloft/rain roof fire caused the death of six firefighters in a Brooklyn, New York, supermarket during daylight hours. There was no roof indication of the massive fire conditions within the large lumberyard that made up the bowstring truss assembly beneath the rain roof. If the fire condition spreads between the original and the flimsy added rain roof, it burns too fast for roof forces to react to rapid failure and resultant flame flashover on the roof`s surface.
Roof areas of older buildings also have renovations that may not be recognized as collapse indicators. If not in the preplan, the vertical ventilation team must notify the commander of the presence of retrofitted air-conditioning units “laid” on top of the roof. The original roof assembly was constructed to withstand only a rain or snow load.
Main thoroughfares that were at ground level in the old days are now elevated highways in the air. How does the store owner get the attention of shoppers passing overhead? You guessed it–signs (billboards) that turn and glow and weigh more than the original roof was designed to support. Sure, the roof may have held it for years, but now fire is rapidly weakening an already weakened roof. Disaster forecast!
Other collapse factors. A local collapse factor surrounds any cellar fire. It is not to say that a cellar fire will cause local collapse of the first floor; however, we must account for additional factors. The fire will be undetected (as said before in this column)–undetected by civilians, causing a delayed alarm, and undetected by us on the fireground. How many times have you said, “Gee, maybe we had better check the cellar” after exhaustive attempts to find the fire on the first floor? The cellar fire burns longer, is basically a ventilation nightmare, and attacks support structures directly. Support structures on other floors usually are protected by some type of ceiling membrane. Fire in more than one floor? Watch the control effort. Are you making rapid headway? Is the fire changing due to engine operations? Outside commanders must continuously get answers to these and other questions about the condition of interior structure supports.
Another location that demands intense risk analysis is fire located within truss assemblies and truss lofts. Truss assemblies are located on every floor today; once fire is within the assembly, rapid failure can occur. Some authors today say that if fire is within the truss assemblies, we must not enter the structure. But, again, that is half a truth. Guidelines should stress on the decision maker the danger of commitments inside such a structure and the need to ensure that the life safety of those inside make the risk of entering worth taking. You can afford to dictate “Outside operations only” if you are sure all life is accounted for. However, how can you abide by such a rule if it`s an early-morning fire in an orphanage? All collapse dangers must be assessed and the decision made on the analysis of risks present. (We will refer to this risk analysis again.)
Fire intensity cannot stand alone as a collapse factor. However, intense fire not affected by handlines and the absence of obvious signs of positive effect over a long period of time are causes for shifting strategy.
Perhaps one of the single greatest reasons for “surprise collapse” on the fireground is the failure of interior teams to recognize obvious collapse indicators that, therefore, are not communicated to the incident commander. Collapse awareness is everyone`s business.
Noises inside structures must be noted, communicated, and investigated. Many live with the romantic notion that noise from a collapse–full or partial–is loud and easily recognizable. Nothing could be further from the truth. Most collapses–at least all that I have been associated with–are accompanied by soft whooshing noises that are too difficult to spell and recognize here. I have had rear enclosure walls leave the scene, five floors of stair landing and the bulkhead of an apartment house land in the basement, bathrooms pancake for six floors, stairs and assemblies fail with people on them–and more. The noise is never great. To the untrained and questioning ear, they can go virtually unnoticed. If you hear a noise, report it.
Floors were never designed to hold a puddle of a few inches or more. Is the floor sagging? Are beams pulling from bearing walls? Are floor joists cracking? Report. Investigate. Assign a priority. Relieve the condition or leave the area.
These are just a few signs–more next time. n
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.
