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Exposure to fine particulate matter (PM 2.5 ) from woodsmoke is a national and global public health concern. While wood heat use is increasing in the Northeast U.S., exposure to woodsmoke in rural valleys in this region remains understudied. Low-cost sensors have recently emerged as a promising strategy to better assess PM 2.5 exposure in communities across the globe. However, real-world, long-term community air monitoring studies deploying low-cost sensors are lacking. Such studies are necessary to validate performance over time for the goals of assessing exposure trends and providing practical guidance to future community-scale projects. Here, we evaluated PM 2.5 community-wide exposure over four years in a rural, woodsmoke impacted community that deployed a Purple Air network. We determined significant differences between the PM 2.5 regulatory reference monitor and Purple Air PM 2.5 concentrations across the community, over multiple heating seasons, at both hourly ( p < 0.01) and 8-hour average time intervals ( p < 0.001). PM 2.5 was especially elevated in the evenings (6 pm to 2 am), with a maximum 1-hour average of 81.7 μg/m 3 and a maximum 8-hour average of 78.7 μg/m 3 . Consistent with other performance evaluations in the literature, we determined Purple Air sensors have low bias after correction (2.4% Normalized Mean Bias Error NMBE , 3.3 μg/m 3 Root Mean Square Error RMSE ). Co-located sensors were reliable in harsh winter conditions for up to three years. We suggest quality assurance, data management, correction model selection, and citizen science partnerships are critical considerations for sensor network deployments aiming to assess long-term exposure and health. • Long-term PM 2.5 exposure data in woodsmoke-impacted U.S. rural valleys are limited • Low-cost sensors are a promising tool for exposure assessment in communities, but real-world data on implementation is needed • We determined significant differences over multiple winters between Purple Air sensors in neighborhoods and the Federal Equivalent Monitor, with elevated PM 2.5 in the evenings (6 pm to 2 am) • Purple Air units provided reliable data for 3 to 4 years in winter conditions using appropriate QA/QC and post-correction models
Traviss et al. (Tue,) studied this question.