Objective - To quantify the threat of firebrand (ember) exposure from WUI fires on structures and structural materials.
What is the new technical idea? Despite the increasing frequency and losses from WUI fires, compared to fires within structures, there has been relatively little research on WUI fire spread. This is especially the case for fires ignited from firebrands (or embers), which is a main cause of structural loss within the WUI. For example, NIST research into WUI fires that occurred in California (2007) , Texas (2011) , and Colorado (2012)  have demonstrated that firebrands (embers) can account for 50% of the ignitions in WUI fires. Research on WUI fires has been difficult, in part, due to the fact that the subject area falls between traditional studies of building fires and forest fires, which in the past has been the responsibility of different branches of the government. However, without research, building codes and standards (namely the WUI-related codes and standards) do not provide adequate protection to structures within the WUI. More specifically, codes and standards do not adequately address the range of exposures during a WUI fire – especially firebrand (ember) exposures.
The major objective for this project is to develop the measurement science to quantify firebrand (ember) exposure during WUI fires. This project will design and develop a device, i.e., referred to as an "emberometer", to enable accurate quantification of critical characteristics of firebrand (ember) exposure, such as flux (m-2s-1 or g/m2s) and energy (e.g., temperature), based upon their importance for solid fuel ignition and technical feasibility. The "emberometer" device will be developed to measure firebrand (ember) exposure in laboratory settings, controlled field experiments, and actual WUI events; however, the focus will be on laboratory scale for FY17.
Advances in measurement science are needed to effectively characterize and identify the conditions and mechanisms that result in a high risk of structure ignition across a range of WUI community types and conditions. Characterizing firebrand (ember) exposure will aid in further developing the WUI Hazard Scale  as well as provide the technical foundation for improvements to WUI-related codes, standards, and standard test methods.
What is the research plan? In FY16, work is ongoing to develop a database reviewing all test methods relevant to WUI, including any that use firebrands (embers) to test for ignition susceptibility of solid fuels. Additionally, work is just beginning on a literature review of research involving firebrands (embers) (developing an endnote library). From this review, work will be performed to identify the various characteristics in which firebrands (embers) and firebrand (ember) showers can differ (e.g., flux, size, mass, intensity) and, to the extent possible, the range of values associated with each of the characteristics.
In FY17, work will be performed to develop a design for the "emberometer" for laboratory settings. Building upon the firebrand (ember) characteristics identified in FY16, these characteristics will be ranked according to their importance for solid fuel ignition. Next, techniques that can be used to measure the ranked characteristics will be identified and documented. Laboratory testing of the measurement techniques will then be conducted to examine the technical feasibility of each approach (for the laboratory setting as well as for controlled field experiments and actual WUI fire events). The main critical factors of firebrands (embers) – based on both importance to solid fuel ignition and technical feasibility – as well as the viable techniques that can be used to measure each factor will be identified. Finally, a design for the emberometer will be developed (i.e., a device that measures all critical factors identified in previous steps) and the design will be documented in a report.
Also in FY17, work will be performed on increasing the range of a bench-scale firebrand (ember) generator capable of producing firebrand (ember) fluxes in various combustion states (e.g. smoldering, flaming or non-reacting particles) to ensure reproducible/flexible firebrand (ember) generation for laboratory settings. This device differs from current generators in that transport of firebrands (embers) can be simplified (e.g. static version with gravity-driven firebrand deposition) and thus alleviate both implementation and safety constraints pertaining to the use of dynamic systems (e.g. wind-driven).
In out years (FY18 and FY19), work will be performed to fabricate and test the "emberometer" design developed for laboratory settings. Once initial testing is complete, a new design will be developed for an "emberometer" that can be used in controlled field experiments and actual WUI fire events (i.e., outside of the laboratory setting). Once fabrication for the "outdoor emberometer" is completed, NIST will identify collaboration/field teams that can employ the emberometer to collect exposure information on firebrands (embers) during field studies, and initial data collection to characterize firebrand (ember) exposure can begin.