An Evaluation of Raspberry Pi-Based Low-Cost PM2.5 Sensors in Western North Carolina

Routine ambient air quality monitoring is mandated by U.S. federal law, but many regions of the U.S. are sparsely monitored due in part to the high cost of regulatory monitors. Low-cost sensors can fill data gaps when it is neither feasible nor cost-effective to expand regulatory monitoring networks. We built several low-cost fine particulate matter (PM2.5) sensors using a Raspberry Pi 4 and the SDS011 particle sensor from Shandong Nova Technology. The sensors were operated in the ambient environment during multiple weeks-long field campaigns in the summer and fall 2022 in Asheville, North Carolina. All sensors were collocated with each other to measure inter-sensor variability. We also collocated our sensors with a PurpleAir PA-II sensor - a commercially available low-cost PM2.5 sensor - and a Federal Equivalent Method BAM PM2.5 monitor maintained by the local air quality agency. Comparisons between the SDS011 and the regulatory monitor in particular will help determine whether our low-cost sensor could supplement existing monitoring networks with useful and reliable information. Our field deployments occurred during a range of weather conditions and seasonal changes in PM2.5 concentrations. High water vapor content is known to affect the performance of optical particle counters such as the SDS011 and PA-II, so we expect high biases during periods of high humidity. We also measured in-situ meteorological variables including humidity and temperature to understand how our sensor performs under varying atmospheric conditions.