This study examines the size distribution and other characteristics of firebrand exposure during the 2007 Angora Fire, a severe Wildland-Urban Interface (WUI) fire in California. Of the 401 houses that received direct interface fire exposure 61% were destroyed and 30% did not burn at all. The ignition of buildings by wind-blown embers, known as firebrands, and the starting of ("^)spot fires("^) in unburned vegetation ahead of wildfires has been observed for centuries and studied extensively for decades. However, it is not yet possible to empirically quantify the exposure severity or describe how many firebrands of what size and over what duration and distance are causing ignition problems of concern. A Seemingly rare opportunity to gather empirical firebrand data from an actual interface fire evolved in the days, immediately following the Angora Fire. Firebrand size distributions are reported and compared to firebrand size distributions from experimental firebrand generation in both recent laboratory building ignition studies conducted by National Institute of Standards and Technology (NIST) and from historical firebrand field studies. Such data is needed to form the basis of effective and appropriate interface fire hazard mitigation measures as well as modeling fire spread. Comparisons are made to current wildfire protection building construction regulations and test standards. The most salient results of this study are the documentation of the consistently small size of firebrands and the close correlation of these of these results with the size of experimentally generated firebrands.
Proceedings Title: Fire and Materials 2011
Conference Dates: January 31-February 2, 2011
Conference Location: San Francisco, CA
Conference Title: 12th International Conference
Pub Type: Conferences
WUI fires, firebrands