Vulnerability of Decking Assemblies to Continuous Firebrand Shower
Samuel L. Manzello, Sayaka Suzuki
In WUI fires, decking assemblies have been observed to be an ignition vulnerability based on post-fire damage surveys. The Office of the State Fire Marshall (OFSM) in California adopted the test method known as State Fire Marshall (SFM) STANDARD 12-7A-4 . The SFM test method is intended to determine the response of decks to firebrand exposure. Namely, a firebrand is simulated by placing a burning wood crib (either Class A, Class B, or Class C firebrand) on top of a section of a deck assembly under an air flow. This test standard does not adequately simulate the processes and conditions observed in real Wildland-Urban Interface (WUI) fires. The dynamic process of multiple firebrands bombarding decking materials as a function of time is not taken into account in this standard. Firebrand showers have been observed in actual WUI fires over and over again . Based on firebrand attack from real WUI fires, it is expected that multiple firebrands would accumulate within gaps/crevices of decking materials. In addition to not simulating a dynamic firebrand attack, no attempt is made to relate the size and mass of the firebrand used in this standard to actual firebrands produced from burning vegetation and structures. There is no evidence to suggest that this test is a worst-case firebrand exposure for decking assemblies.