Laboratory Analysis of VOC Emissions from Structural Materials in Wildland-Urban Interface Fires

The wildland-urban interface (WUI) has grown in recent decades at the same time as wildfires have expanded in range and scope. Fires at the WUI are therefore more common, and structural materials make up more of the wildfire fuel mass. While emissions from biomass fires are fairly well understood, volatile organic compound (VOC) emissions from structural fires are less constrained. In this study, we perform measurements of VOC emissions from small-scale laboratory burns of 18 different structural materials across 78 experiments using a Vocus proton-transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) to better understand these unique emissions. We calculate emission factors for 73 VOCs across all materials, including aromatics and polycyclic aromatic hydrocarbons (PAHs). We compare the emissions from both flaming and pyrolysis, which separate the processes of direct release of VOCs from combustion formation. Mass spectra comparisons were used to qualitatively highlight high-emission compounds across materials and identify notable emissions (e.g., nylon monomers) and potential tracers (e.g., halogen species) for WUI fires. Using these data, the emissions from a whole-house fire were compared with those from an equivalent mass of wood, and we found that some aromatic and nitrile species may be suitable WUI fire tracers.