Characteristics of Firebrands Collected from Actual Urban Fires

The characteristics of firebrands collected from a recent urban fire in Japan are described. Specifically, this fire broke out from a Chinese restaurant in Itoigawa-city, Niigata, Japan on December 22^nd 2016. On the day of the fire, strong winds resulted in rapid fire spread. With the presence of an average wind speed of 9 m/s, the fire quickly spread, resulting in the damage of 147 structures, with 120 of 147 destroyed. The fire was extinguished more than 30 hours later. During the fire, firebrands were observed and 10 spot fires were reported. After the fire, investigations were performed and firebrands were collected from the burn site. The size and the mass of firebrands were measured and compared with the available literature data. It was observed that more than 60 % of the collected firebrands had less than 0.10 g mass and 2.0 cm² projected area and the size and the mass of firebrands were independent of the location. The size and the mass of firebrands from this fire were similar to those from another urban fire under similar wind speed and were also compared to those produced from a firebrand generator. The firebrand data set presented here provided valuable insights into how firebrands are generated from structures in actual urban fires. Finally, the description on how a firebrand generator may be used to produce firebrands similar to urban fires yields an important advancement to begin to study such complex phenomena in the laboratory.