2024 No https://doi.org/10.1038/s41370-024-00677-8 Stampfer, Orly North America Experimental Exposure Study Students Staff Particulate Matter (PM) Low-cost sensors Wildfire smoke. Particulate matter (PM) Schools Indoor air quality This study measured PM2.5 at four Washington schools using low-cost sensors and gravimetric samplers. Results showed large within-school variation and found that frequent, multi-day handheld monitoring improves indoor/outdoor ratio estimates during smoke events.