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Thermal characterization of firebrand piles

Author(s): Raquel S. P. Hakes, Hamed Salehizadeh, Matthew J. Weston-Dawkes, Michael J. Gollner
Year Published: 2019

The cause of the majority of structure losses in wildland-urban interface fires is ignition via firebrands, small pieces of burning material generated from burning vegetation and structures. To understand the mechanism of these losses, small-scale experiments designed to capture heating from firebrand piles and to describe the process of ignition were conducted using laboratory-fabricated cylindrical wooden firebrands. Two heat flux measurement methods were compared, and the influences of firebrand diameter, pile mass, and wind on heating from firebrand piles were explored. Diameter had little effect on heating, pile mass a moderate effect, and wind a large effect. Peak heat fluxes showed distinct differences between heat fluxes produced by firebrand piles as opposed to individual firebrands, which have been studied exclusively on the small-scale in the past. Above a critical mass, piles did not produce higher heat fluxes; however, they heated fuels for an increasingly longer duration and over a larger area. Water-cooled heat flux gauges provided reliable heat flux measurements for large firebrand piles and an array of thin-skin calorimeters indicated significant spatial variation in heat flux. A recipient fuel transitioned from smoldering to flaming under an adequate wind speed soon after a firebrand pile was deposited on its surface.

Citation: Hakes, Raquel S.P.; Salehizadeh, Hamed; Weston-Dawkes, Matthew J.; Gollner, Michael J. 2019. Thermal characterization of firebrand piles. Fire Safety Journal 104:34-42. https://doi.org/10.1016/j.firesaf.2018.10.002
Topic(s): Fire Behavior, Risk, Risk assessment, Wildland Urban Interface, Wildland Urban Interface
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 19225
FRAMES RCS number: 56783
Record updated: Mar 27, 2019