Laboratory Quantification of Emissions from Wildland-Urban Interface Fuels Using Fourier-Transform Infrared Spectroscopy.

Emissions from eight common wildland-urban interface (WUI) fuels were quantified using Fourier-transform infrared spectroscopy under varying oxygen concentrations (0, 14, 21%) and heat fluxes (25, 50 kW/m2). Emission factors for carbon monoxide (CO), carbon dioxide (CO2), and other gaseous and particulate effluents varied significantly across these conditions. By implementing a new Toxicity Score method, polyvinyl chloride was identified as the most hazardous fuel, followed by asphalt shingles and vinyl plank flooring under smoldering conditions at 21% oxygen concentration. Hydrogen chloride was the dominant toxicant across all test conditions, while formaldehyde was a major contributor at 25 kW/m2 and carbon monoxide became increasingly significant at 50 kW/m2. Hydrocarbon emissions increased markedly under pyrolysis conditions, particularly from synthetic materials like asphalt shingles. Notably, total particulate matter emissions varied under different conditions and were also influenced by fuel consumption efficiency. These findings contribute to improved wildfire emission models and underscore the need to consider diverse environmental conditions in future WUI fire research.