Emissions from Structure Fires: Overview of BHASMA and Results for CO ₂ and Select Pollutants by Fuel, Combustion Mode, and Scale

With ∼50 million houses in the US located at the wildland-urban interface (WUI) and wildfire activity on the rise, there is a concern that structure fires might be a key source of air pollutants in WUI regions. We report on structure fire experiments performed as part of the Burning Homes And Structural MAterials (BHASMA) project. More than 70 small-scale experiments were performed on 19 different fuels and fuel complexes, representing lumber, processed wood, insulation, carpet, roofing, electrical sheathing, and flooring. More than 20 large-scale experiments were performed on different sizes and packing densities of a fuel test crib composed of lumber, processed wood, gypsum board, and plastics. Emission factors (EFs) for CO₂, CO, and CH₄ at the same combustion efficiency (CE) did not vary strongly with fuel category or fire scale and were generally consistent with emissions reported in the literature for biomass burning. EFs for PM_2.5, organic aerosol, and soot for non-wood-based fuels under flaming conditions were higher than those from wood-based fuels, with soot emissions being 10-fold higher. Overall, we find that structure fires can be similar to vegetation fires for some pollutants (e.g., CO) but not all pollutants (e.g., soot). Our work contributes to the understanding of emissions and environmental impacts from WUI fires.