Timescales of Gaseous Smoke Contamination Indoors from Real and Simulated Wildland-Urban Interface (WUI) Fires

Fires occurring at the wildland-urban interface (WUI) can produce smoke that contains unique chemicals from the combustion of urban structures, which can then contaminate nearby buildings and affect indoor air quality. Assessing property loss and possible occupant exposure to persistent contamination from WUI smoke is challenging, in part, because of a lack of measurements detailing chemical contamination in real indoor environments after WUI events. Here we mimic contamination from a WUI fire by repeatedly exposing a test house to smoke from combustion of residential building surrogates and measure the persistence of volatile non-methane organic gas (NMOG) contamination. Over the 1.5-month experimental period we observed an increase in emission rates of 31 NMOGs indicating the formation of surface reservoirs indoors that increase with subsequent burns. We observe off-gassing timescales of less than 10 days for many highly volatile NMOGs like acetonitrile, acrylonitrile, and styrene. Other NMOGs, like naphthalene and C12 aromatics, took longer than 10 days to off-gas and show emissions persistently elevated above background for at least three months after the end of the experiments. The NMOG emissions from contamination in the test house were much lower compared to a house affected by the Marshall Fire in Colorado. However, NMOG off-gassing times measured in the test house were longer.