Laboratory Evaluation of the Alphasense Opc-N3, and the Plantower PMS5003 and PMS6003 Sensors

KAMALJEET KAUR, Kerry Kelly, University of Utah

     Abstract Number: 56
     Working Group: Instrumentation and Methods

Abstract
Numerous studies link adverse human health effects to ambient levels of particulate matter (PM), although fewer studies have evaluated the health effects of coarse PM (diameter larger than 2.5 µm). Coarse PM measurements are also scarcer than PM2.5 measurements. Low-cost PM sensors, such as the Plantower PMS5003, have been used complement regulatory measurements to provide highly resolved estimates of PM2.5 concentration. However, most low-cost PM sensors are ineffective at measuring coarse PM. In contrast, the Alphasense OPCs have shown promise in detecting coarse PM and have been used in the field to measure PM10 concentrations. Despite field evaluations being critical for understanding sensor performance under environmentally relevant conditions, they provide limited information about sensor response characteristics, which are essential for determining factors that may affect sensor measurements and contribute to inter-sensor variability. This study aims to systematically evaluate the response of the Alphasense OPC-N3, and the Plantower PMS 5003 and 6003 to monodisperse particles of various diameters generated by a flow-focusing monodisperse aerosol generator and compared to an aerodynamic particle sizer (APS). The study evaluated nine different OPCs, three PMS5003s, and four 6003s. The Plantower PMS 5003s and PMS 6003s detected all particle sizes but assigned all particles to the smallest size bin. The OPC-N3s detected all particle sizes and exhibited a coefficient of variance of less than 10% compared to the APS, although they tended to overestimate particle diameter slightly. The OPCs generally underestimated particle concentration compared to the APS (bias between 7 to -75%) and inter-sensor variability that increased with particle diameter (19.4% for 2 µm and 34.2% for 10 µm). The OPC-N3 laser wavelength varied between 600-650 nm, and this variation was correlated with inter-sensor variability of the mean diameter measurements, while the flow rate reported by the OPC affected the inter-sensor variability in the number concentration.