On the use of a firebrand generator to investigate the ignition of structures in WUI fires

An experimental apparatus has been constructed to generate a controlled and repeatable size and mass distribution of glowing firebrands. The present study reports on a series of experiments conducted in order to characterize the performance of this firebrand generator. Firebrand generator characterization and subsequent structural ignition experiments were performed at the Fire Research Wind Tunnel Facility (FRWTF) at the Building Research Institute (BRI) in Tsukuba, Japan. The firebrand generator was fed with mulch generated from Korean Pine trees. To produce repeatable initial conditions for each experiment, the Korean Pine mulch was sorted using a series of filters prior to being loaded into the firebrand generator. The size and mass distribution of firebrands produced from the generator was tuned to be representative of firebrands produced from burning trees. After the size and mass distribution of firebrands was characterized, the device was then used to direct firebrand fluxes towards a structure installed inside the FRWTF. A gable vent was installed on the front face of the structure and three different steel screens were installed behind the gable vent to ascertain the ability of the screen to block firebrands from penetrating into the structure. The mechanism of firebrand penetration through screens was observed for the first time. The firebrands were not quenched by the presence of the screen and would continue to burn until they were able to fit through the screen opening. Results of the study are presented and discussed.