Aerosol Emission Factors for Structural Fuels in Wildland-Urban-Interface Fires

KEVIN RIDGWAY, Anna Helfrich, Lily Cast, Amy P. Sullivan, Aika Davis, Ryan Falkenstein-Smith, Thomas Cleary, Rodney Bryant, Mathew Bundy, Christian L'Orange, Shantanu Jathar, Colorado State University

     Abstract Number: 248
     Working Group: Burning Questions of Aerosol Emissions, Chemistry, and Impacts from Wildland-Urban Interface (WUI) Fires

Abstract
With nearly 50 million houses in the United States located at the wildland-urban interface (WUI) and wildfire frequency and activity on the rise, there is a growing concern that wildfire-related structure fires might be an important source of air pollutants in WUI regions, with implications for air quality and public health. However, aerosol emissions from structure fires are poorly understood and what we do understand remains fragmented and incomplete. The Burning Homes And Structural Materials (BHASMA) campaign studied emissions from a variety of structural fuels under different combustion modes (pyrolysis and flaming) and fire scales (0.5-250 kW) in an effort to quantify fuel-specific emission factors. Around 100 experiments were conducted with over 17 different fuels, including: lumber (e.g. southern yellow pine), engineered wood products (e.g., oriented strand board), insulation (e.g. polyurethane foam), textiles (e.g. polyester carpet), conduit (polyvinyl chloride), siding (e.g. cement fiberboard). Additionally, fuel mixtures representative of residential structures were combusted to compare mixed-fuel emission factors with individual fuels. Differences in emission factors are evident between fuel type and combustion efficiency, often ranging 1-2 orders of magnitude for bulk pollutants: PM2.5 and organic aerosol (OA). Considering non-lumber materials as a 30% fraction by mass for a structure increases the net emissions by a factor of two for PM2.5, three for OA and nearly five for elemental carbon (EC, soot). Ongoing work is focused on identifying fuel-specific signature species based on a detailed analysis of ions, saccharides, and elemental species (e.g. ammonium, levoglucosan, zinc, chromium, iron – for biomass v. non-biomass fuel identification) and comparing species-resolved emission factors with literature data. Our work will contribute to a more detailed understanding of pollutant exposure for first-responders, evacuees, and down-wind communities affected by WUI fires.