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Exterior exposures are a major concern for many fire departments. Fire departments that protect congested urban and suburban areas must deal with structures that are built alongside one another.
With buildings that are attached to one another or separated by only a few feet, fire extension into adjoining or nearby structures must be considered an early possibility. In these settings, hesitation can let fire not only occupy one, but three buildings in a short amount of time.
In order for incident commanders to direct efficient and effective fireground operations, officers must identify and prioritize protection of exposure buildings from a number of factors.
The life hazard – specifically those nearest
Buildings must be prioritized based on “the most severely threatened exposure” versus “the most severely threatened life exposure.” This is not a play on words; there is a difference.
Exterior exposure concerns must immediately focus on determining the “most severely threatened exposure” versus the “most severely threatened life exposure.” The most severely exposed or closest building may not necessarily be the one that receives the incident commander’s initial attention. Initial courses of action must be based on any threat to life in nearby or attached properties.
The best way to illustrate this thought is with an example. Let’s say you arrive at a well-involved structure severely exposing a nearby vacant, two-story frame building on the west side and a closely spaced two-story, occupied wood frame on the east side. Now, even though the building to the west is referenced as being severely exposed and closer to the fire building, the occupied building on the east side would warrant the initial exposure protection simply based on the potential life hazard.
As simple as this example is to identify with, everything that we do is based on the life hazard size-up. Additional resources can always be delegated as the incident commander sees fit, but your initial course of action is always based on the life hazard.
Is the exposure attached or separated, and by how much? Buildings that are attached or separated by narrow alleyways are immediate concerns for responding firefighters. Due to their proximity to one another, resources will have to be assigned to check and protect the buildings from any fire extension.
Buildings whose exterior sheathing/siding is combustible can also enhance the fire’s spread from one building to another. Buildings covered in wood or asphalt siding will warrant earlier consideration than those made of brick or stone. Firehouse® Contributing Editor Chief Vincent Dunn of the FDNY has often stated that the combustible exterior siding of a structure can present a seventh side of fire travel. Not only can the involvement of the siding spread up and back into the building itself, but it can quickly spread fire to a nearby exposure building.
Jersey City, NJ, firefighters were confronted with a fire that extended to a building’s exterior asphalt siding and that spread to the asphalt siding of an exposure building. A well-supplied hoseline will quickly darken down the exterior fire. But, the problem with this fire, as with all asphalt-siding fires, is the energy this fire can produce before you get a hoseline stretched and operating.
Asphalt siding is a hydrocarbon-based material; thus the term and comparison used by many as “gasoline siding.” The amount of heat and energy being produced will quickly push fire into buildings through sheathing, windows and roof overhangs. Although an exterior hose stream will extinguish the majority of the outside fire quickly, the energy may have already pushed fire beyond the siding and into the structure.