FSRI Completes Initial Structure-to-Structure Fire Spread Experiments
The Fire Safety Research Institute (FSRI), part of UL Research Institutes, completed initial experiments for the Heat Transfer from Structure Fires research project at UL’s fire laboratories in Northbrook, IL. Three interconnected phases of experiments were designed to understand the mechanisms for structure-to-structure fire spread.
Phase One: Examining Radiant Heat Transfer to Exterior Building Materials
The first phase of experiments examined the ignition potential and burning behavior of various building material samples—including roofing, decking, siding, and windows—over a range of heat flux exposures. Researchers used a 6 megawatt fire source generated by a heptane spray burner located under an oxygen consumption calorimeter for these experiments. The 8 x 8 inch (20 x 20 centimeter) building material samples were exposed to approximate heat fluxes of 10, 20, and 30 kW/m² for 7–9 minutes.
Phase Two: Characterizing Impact of Cladding Assemblies on Heat Flux Exposure from Post-Flashover Compartment Fire
During the second phase of experiments, researchers quantified the heat flux exposure at various distances from a post-flashover compartment fire that had spread to an exterior wall. Interior dimensions of the compartment were 12 feet (3.7 meters) wide by 8 feet (2.4 meters) deep by 8 feet (2.4 meters) high, and two openings were located on its front to simulate an open sliding glass door and window. A facade wall was attached to the compartment and was equipped with three different cladding assemblies—vinyl over expanded polystyrene insulation, T1-11 wood paneling, and fiber cement board lap siding–to examine the contribution of the assemblies on the measured exposures. Two replicate experiments were performed with each siding type.
The fuel load in the compartment consisted of two sofas on top of carpet and padding and two layers of plywood along the walls and ceiling. Each experiment began with the ignition of one sofa. Researchers allowed the fire to transition through flashover to simulate fire spread from the interior to the exterior of a structure. For each experiment, the heat flux exposure was quantified by an array of heat flux gauges positioned at various locations in front of the source structure, and the heat release rate profile of the fire was obtained via oxygen consumption calorimetry.
Phase Three: Examining Fire Spread Potential from a Post-Flashover Compartment Fire to a Target Structure
Researchers used the compartment and façade configuration characterized in the second phase as the source fire during the third phase of experiments. A target facade wall containing two windows was positioned in front of the source structure. Based on the results from the first two phases, researchers implemented a 16-foot separation distance between the source and target structures.
The experiments examined different cladding assemblies installed on the target wall as well as the impact of different intermediate fuels—including a shed, car, and attached deck—between the structures on the potential for fire spread to the target structure. Additionally, researchers quantified the heat transfer through windows and subsequent window failure during these experiments.
Researchers will present the visual observations during each phase of experiments along with a detailed analysis of the measurement data in future peer-reviewed publications. Findings from this project will have critical implications for establishing proper control measures and supporting fire and building code development in urban and wildland urban interface environments.
