Abstract View
A Comprehensive Test Standard for Indoor Air Quality Low-Cost PM2.5 Sensors
WILTON MUI, Xiaobi M. Kuang, Sahil Bhandari, Vasileios Papapostolou, Andrea Polidori, South Coast Air Quality Management District
Abstract Number: 453
Working Group: Aerosol Standards
Abstract
Low-cost air sensors are a relatively new class of air pollutant monitoring devices that typically have characteristics of being compact, lightweight, portable, simple to operate, and roughly one to two orders of magnitude less expensive than research-grade or reference-grade instruments targeting the same pollutant. Despite these advantages, there are uncertainties about data quality and sensor performance. The Air Quality Sensor Performance Evaluation Center (AQ-SPEC) at the South Coast Air Quality Management District has previously published some of the few existing performance evaluation field and laboratory test methods for low-cost sensors targeting particulate matter smaller than 2.5 micrometers in diameter (PM2.5). More recently, a new comprehensive test standard for indoor-specific low-cost PM2.5 sensors has been developed in collaboration with ASTM International, and its relevance coincides with pandemic-related concerns of indoor particle concentrations. The new test standard is comprised of five phases conducted in an environmental test chamber with reference-grade monitors: 1) initial PM2.5 concentration ramps using both an inorganic and an organic particle surrogate, 2) performance characterization across a range of temperature and relative humidity conditions, 3) investigating the effect of coarse particulate matter as an interferent, 4) repeated temperature cycles to simulate long-term operation, and 5) a final PM2.5 concentration ramp using only the inorganic particle surrogate. Four sets of low-cost sensor models in triplicate were pilot-tested with this new PM2.5 performance test standard. One sensor model tested accurately reported PM2.5 values in the initial concentration ramp, while the other three models overestimated PM2.5 values by about a factor of two; nonetheless all four models tested showed very high correlation with reference measurements (R2 > 0.99). A variety of additional performance metrics to provide insights on other aspects of sensor performance are also deduced from the data, such as accuracy, precision, bias, climate susceptibility, interference, drift, and data recovery.