Impact of Wildfire Smoke on Indoor Air Quality in Interior Alaska: A Case Study

Residential areas are increasingly impacted by wildfire smoke that causes hazardous local ambient air quality conditions which also impacts the quality of indoor air as smoke particles penetrate the building envelope or the HVAC filtration systems. In this work we investigate the impact of wildfire-affected poor ambient air quality on indoor air particulate matter during a wildfire episode in June 2015 in interior Alaska. We measured size-resolved (0.3 µm – 10 µm) particle number counts (PNC; numbers/cm 3 ) and calculated particle mass concentrations (PMC; µg/m 3 ) outside and inside of three buildings in Fairbanks, Alaska during this summer wildfire event. For comparison, the measurements were repeated during a no-wildfire time window in summer 2017. Our results show that the fire episode increased the total PNC by factors of 189.4 -244 in the outdoor air and by 19.5-150 in the indoor air compared to the total PNC measured during a nonfire season. The PNC was primarily dominated by particles 0.31 µm (>99%) at all locations during the fire season, whereas the PMC was dominated by particles in the size range from 2.5 - 0 µm (40-67%). The indoor to outdoor ratio (I/O) of PNC during the fire season was significantly lower for an unventilated building (I/O = 0.13±0.001) as compared to those with active (filtered) ventilation (I/O = 0.76±0.11 and 0.62±0.02), suggesting that lower efficiency filters (lower than MERV 11) often used in residential and public buildings may not control the infiltration of smaller smoke particles during a wildfire event. Data from this study suggests that sheltering in a closed, non-ventilated building can be an effective strategy to reduce exposure to particulate matter given that there are no significant indoor source(s) of particulates and that the air leakage is insignificant.

• Citation - Dev, S., D. Barnes, A. Kadir, S. Aggarwal. In Review. Outdoor and indoor concentrations of size-resolved particulate matter during a wildfire episode in Interior Alaska and the impact of ventilation. Science of the Total Environment.