AEROSOL EMISSIONS FACTORS FOR STRUCTURAL FUELS IN WILDLAND-URBAN-INTERFACE 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 implica- tions 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 fu- els 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 repre- sentative 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 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). Additional work focused on identifying fuel-specific signature species based on a detailed analysis of ions, sugars (saccharides), and elemental species (e.g. ammonium, levoglucosan, zinc, chromium, iron – for biomass v. non-biomass fuel identification) and comparing species-resolved emission fac- tors with literature data. This work will contribute to a more detailed understanding of pollutant exposure for first-responders, evacuees, and down-wind communities affected by WUI fires.