Indoor Building Materials as Reservoirs for Prolonged Wildfire Sourced VOC Exposure

RACHEL HURLEY, Shichao Liu, Anita Avery, Manjula Canagaratna, Chenyang Bi, Worcester Polytechnic Institute

     Abstract Number: 279
     Working Group: Burning Questions of Aerosol Emissions, Chemistry, and Impacts from Wildland-Urban Interface (WUI) Fires

Abstract
Wildfire smoke can severely damage indoor materials by infiltrating indoors and absorbing on surfaces. Volatile organic compounds (VOCs) may re-emit from smoke-contaminated building materials and persist for weeks to months indoors, posing long-term exposure risks. However, the intensity and duration of indoor exposure, governed by re-emission rate and timescale, respectively, remain poorly understood. The objective of this work is to better understand the human exposure to VOCs re-emitted from smoke-contaminated building materials. Six materials—drywall, painted drywall, granite, hickory flooring, carpet, and aluminum—were soaked in burned pine needle lab-generated smoke for 40 minutes with particles removed with an in-line HEPA filter. VOC re-emission from smoke-contaminated materials were monitored in a rapid emission chamber using a Vocus Chemical Ionization Time-of-Flight Mass Spectrometer (Vocus CI-ToF-MS) with NH4+ as the reagent ion. Micro-computed tomography quantified material porosity. A mechanistic model will be developed to link key emission parameters to re-emission rate and timescale.

We found that re-emission rates and timescales are governed by the material’s porosity and are associated with the physiochemical properties of the VOCs, such as volatility and solubility. There are significant impacts of material type on the maximum re-emission concentration with acetaldehyde and furfural being the most abundant compounds across all materials. Drywall (bare and painted) exhibited re-emission levels up to three orders of magnitude higher than impervious aluminum, emphasizing the importance of pore space in VOC transport. Interestingly, painted drywall retained fewer VOCs and showed faster re-emission compared to bare drywall, likely due to the paint layer’s low porosity acting as a barrier. However, for some polar compounds, the maximum re-emission for wood and painted drywall were higher than pure drywall. The VOC decay profiles in chamber tests provide critical emission parameters to fit a mechanistic models predicting re-emission and human exposure after wildfire smoke infiltrates indoors.