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Enabling Exposure Comparison for Firebrand Showers Generated During Wildland-Urban Interface (WUI) Fires



Nicolas Bouvet, Eric Link, Savannah Wessies, Stephen Fink


Firebrand showers are known for their devastating effects throughout Wildland-Urban Interface (WUI) communities threatened by wildfires. In 2019, the Insurance Institute for Business and Home Safety (IBHS) released an online statement echoing many field observations, reporting that, "during wildfires, as many as 90 % of homes and buildings damaged or destroyed were first ignited by embers or other fires set by embers and not the main wildland fire front". This staggering statistic stresses the importance of developing the measurement science to perform in situ characterization of firebrand showers. Recently, NIST has designed and fabricated an instrumentation prototype, referred to as Emberometer, aiming at investigating airborne firebrand flows. This device merges two imaging techniques: 3D Particle Velocimetry (3D-PTV) for the mapping of individual firebrand trajectories and 3D Particle Shape Reconstruction (3D-PSR) based on the Visual Hull concept in order to fully characterize complex, combusting particle-laden flows, in both space and time. An improved version of the emberometer, geared towards field use with enhanced firebrand detection capability and data processing pipelines is presented in this work. This new system is leveraged to study, in outdoor settings, a firebrand shower artificially generated that contains mixed amounts of smoldering and flaming particles. The firebrand tracking efficiency is carefully monitored and the performance of the firebrand trajectory recombination procedure (occurring whenever broken trajectories are identified) is assessed on a data subset. A 3D graphical representation, referred to as "firebrand rose", which offers convenient exposure visualization independent of any specific observation direction, is used to support quantitative comparison with a similar test case (same experimental configuration but indoor settings), with both cumulative particle count and 3D particle flux as reference metrics. Differences observed between the two particle-laden flows are highlighted. This approach formalizes, for the first time, a framework for systematic comparison of 3D firebrand exposures, a major step towards exposure severity ranking.
Proceedings Title
Proceedings of the 13th United States National Combustion Meeting
Conference Dates
March 19-22, 2023
Conference Location
College Station, TX, US
Conference Title
13th United States National Combustion Meeting


Firebrands, Wildland-Urban Interface (WUI) Fire, 3D Diagnostics, Exposure Characterization


Bouvet, N. , Link, E. , Wessies, S. and Fink, S. (2023), Enabling Exposure Comparison for Firebrand Showers Generated During Wildland-Urban Interface (WUI) Fires, Proceedings of the 13th United States National Combustion Meeting, College Station, TX, US, [online], (Accessed June 15, 2024)


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Created March 19, 2023, Updated December 4, 2023