Field and laboratory evaluation of PurpleAir low-cost aerosol sensors in monitoring indoor airborne particles

Due to the adverse health effects of residential air contaminants, there have been increased efforts to monitor indoor particulate matter (PM) concentration using low-cost sensors. However, little information is available about the performance of low-cost sensors in monitoring indoor aerosols. We established a research framework to examine the performance of a widely used low-cost sensor in the U.S. (PurpleAir) along with two research-grade light scattering sensors (Grimm 11-A, Sidepak AM520) in a laboratory chamber and a full-scale residential testbed. The results show that low-cost sensors can yield relatively high intra-model consistency for mass concentrations; however, the consistency is lower when measuring particles >1 μm than research-grade sensors. Regression analysis with research-grade sensors shows higher linearity for mass concentration than number concentration. These trends of mass and number concentrations are likely attributed to the size selectivity of Plantower PMS5003 sensor in PurpleAir that constrains the number fractions of specific particle size bins. The results also show that concentration discrepancy between the low-cost sensor and research-grade sensor increases as indoor mass concentration increases, suggesting that sensor quality assurance is needed for episodic indoor emission events that lead to elevated PM_2.5 concentrations (>100 μg m⁻³).