Article and photos by Gregory Havel
Emergency services supervisors are assumed to hold these positions because they are better trained and better educated than the majority of their organization members. We can hope that they have the fortitude to assume the role of “designated grown-up” when things become chaotic at the station or at the scene of an emergency. These statements should be true at all levels, from team leader or company officer through chief officers, including the chief of the department and incident commander.
Combustible concealed spaces (photo 1) are found in Type V (wood-frame) and Type III (ordinary or brick-and-joist) construction. These spaces may have combustible surfaces on all sides, as in a floor-ceiling assembly of wood joists, wood subfloor, and lath-and-plaster ceiling. These spaces may have some noncombustible surfaces, as in a wall assembly of wood studs covered with gypsum drywall board (photo 1). They may sometimes be found in Type II (noncombustible) construction in nonload-bearing interior partitions with wood studs. Fire extending into a combustible concealed space will spread rapidly on the combustible surfaces and can break out into rooms at a distance from the room of fire origin. These spaces can also accumulate gases and vapors resulting from pyrolysis and combustion, which have too little oxygen to burn and which can burn explosively (backdraft) when oxygen is added.
Noncombustible concealed spaces (photo 2) are usually found in buildings of Type I (fire resistive) and Type II (noncombustible) construction. These include spaces completely enclosed by concrete or masonry and spaces enclosed by other noncombustible materials like gypsum drywall board and steel studs (photo 3). Although these spaces do not burn, they can accumulate gases and vapors resulting from pyrolysis and combustion, which have too little oxygen to burn and which can burn explosively when oxygen is added. They can also act as ducts to carry flame and other products of combustion to other parts of the building.
Ineffective supervision may overlook the presence of concealed spaces and the potential for rapid fire spread and for rapid structural collapse if the building uses manufactured wood products and trusses.
The flip side of the ineffective supervision coin is complacency. Whether our supervision is effective or not, usually nothing bad happens to us at our incidents. We get away with so much so often that we believe that this way is the acceptable procedure. Yet, there is always one incident that makes the news—the one where concealed spaces and fire behavior inside them are the key to successful incident outcome—and those factors either were not included or were not given sufficient weight in size-up and in the incident action plan.
Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor's degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC.
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Subjects: Building construction for firefighters
FE Category: Prevention and Protection, Building Construction