Correction of PM 2.5 underestimation in low-cost sensors under elevated dust loading using only sensor measurements

Abstract. The Plantower PMS5003/6003 sensor is widely used for low-cost monitoring of particulate matter (PM), but it substantially underestimates PM2. 5 and PM10 during periods of elevated dust loading, when the particle size distribution is dominated by particles > 1 µm in diameter. This limitation is especially critical in the arid regions, such as the western United States, where windblown dust frequently degrades air quality, visibility, and public health. Accurate estimation of PM2. 5 and PM10 concentrations during periods dominated by dust typically relies on federal reference or equivalent methods (FRM/FEM), but these resources have limited spatial resolution. This study investigates whether PMS5003/6003 measurements alone can be used to detect and to bias correct for these dust-dominant PM conditions. We analyzed measurements from 109 PMS sensors collocated or near 75 U. S. EPA monitoring sites with hourly FEM PM2. 5 and/or PM10 between January 2017 to May 2025. Two cutoff thresholds (threshold1 and threshold2) were developed using relative humidity and the sensor-reported ratio of coarse (2. 5–10 µm) to submicron (0. 3–1 µm) mass concentration to identify potential periods dominated by dust when the PMS sensor underestimated PM2. 5 concentration. The thresholds can be used in real time, relying on the preceding 336 hourly measurements (consistent with PurpleAir's public archive display). To improve PM2. 5 estimates from the PMS sensor (pm2. 5ₐlt, a common correction for Plantower PMS measurements reported by PurpleAir), this study used pm2. 5ₐlt measurements identified as potential dust-dominated periods to develop a correction factor through non-linear regression. This correction reduced the mean bias error between PMS PM2. 5 estimates (pm2. 5ₐlt) and FEM PM2. 5 by approximately 50 % for 97 sensors, and reduced the root mean square error by approximately 30 % for 84 sensors. This framework enhances the utility of PMS5003/6003 measurements during periods of elevated dust loading, extending monitoring capabilities in regions where regulatory coverage is limited.