Effects of dust loading on the long-term performance of portable HEPA air cleaner to woodsmoke – A laboratory investigation

Abstract

Portable air cleaners (PACs) equipped with high-efficiency particulate air (HEPA) filters are recommended to reduce indoor particulate matter (PM) exposure from wildfire smoke, particularly in regions like the Pacific Northwest, where seasonal wildfires affect air quality. While many studies have evaluated the long-term effectiveness of HEPA PACs, few have focused on the effects of dust loading and their performance in filtering woodsmoke over extended periods. This study investigated the impact of filter dust loading on the performance of a HEPA PAC (Winix C535, Winix America) in reducing woodsmoke particles. Filters were pre-loaded with varying amounts of ASHRAE ISO 12103–1 A2 fine test dust, and an exposure chamber was used to assess clean air delivery rate (CADR), airflow rate, and power consumption. Results indicated a significant decline in PAC performance with increasing filter loading, highlighting the importance of regular filter replacements to maintain effective operation. Based on simulations considering dynamic indoor PM_2.5 concentration, in a typical scenario with a 90-m² room, baseline PM_2.5 emission rates, and continuous operation at fan speed Level 2 (5-year mean indoor PM_2.5: 2.99 μg/m³), it would take over 5 years for the PAC filters to accumulate 46 g of dust – an amount associated with a significant drop in CADR observed in the study. These findings suggest that the commonly recommended 1-year replacement schedule by manufacturers may be overly conservative for such conditions. By utilizing indoor air quality sensors to monitor PM concentrations, users can tailor filter replacement schedules to maintain optimal PAC performance in real-world environments.