Impact of Wildfire Smoke PM2.5 on Indoor Air Quality of Public Buildings on a University Campus

With increasing wildfire events impacting many regions worldwide, understanding and mitigating the effects of wildfire smoke on indoor air quality (IAQ) in public buildings are essential for protecting occupant health. This study investigated the impact of wildfire smoke on the IAQ across 24 campus buildings in Alberta, Canada, representing public spaces with varied ventilation systems. Using a network of low-cost sensors to monitor indoor PM_2.5, the study identified significant spikes during wildfire smoke events, with 71% of buildings exceeding the Canadian Ambient Air Quality Standards daily limit of 27 μg/m³. The buildings had mechanical ventilation systems with filters with different Minimum Efficiency Reporting Value (MERV) ratings. MERV13 filters were found to be more efficient at capturing PM_2.5 particles, resulting in lower indoor/outdoor PM_2.5 ratios (0.12 ± 0.07) compared to MERV8 filters (0.28 ± 0.14). Buildings with air change rates (ACH) ranging from 5 to 15 per hour exhibited different infiltration patterns, with higher ACH generally leading to elevated indoor PM_2.5 concentrations during wildfire events. This highlights the need to balance ventilation and pollutant infiltration by optimizing ACH rates and filtration efficiency to reduce indoor PM_2.5. The trajectory-fire interception method, combined with satellite data, enhanced the identification of wildfire-influenced periods, contributing to a better understanding of smoke infiltration dynamics. These findings underscore that even advanced filtration and ventilation systems alone may not ensure a healthy IAQ during extreme pollution. Real-time pollutant measurements are crucial for effective IAQ management. The findings offer valuable insights for building administrators and policymakers, helping them develop strategies to mitigate the effects of wildfire smoke and to support healthier indoor environments during wildfire seasons.