Assessing low-cost purple air particulate matter sensors

Abstract

Wells, Heather. Masters of Environmental Assessment. Assessing Low-Cost Purple Air Particulate Matter Sensors

With technological advances, low-cost light scattering particulate matter (PM) sensors have come into more prevalent use. They operate by sensing laser light scattering by particles. The

scattered light correlates to particle count, and then sensor algorithms can determine the size- selective PM concentration based on the intensity of the light and assumptions about average

particle density. Low-cost sensors are not as accurate as Federal Reference Methods (FRMs), with concentrations having lower accuracy and precision. In order to be able to evaluate air quality using low-cost sensors, it is necessary to test reproducibility of the data. In this study, four PurpleAir low-cost sensors were collocated with a Federal Reference Method to measure PM in a chamber with a wood stove as the source. A data correction scheme for the PurpleAir sensors was developed. While the PurpleAir sensors had high correlations with the tapered element oscillating microbalance (TEOM) reference instrument, their concentrations were roughly 50% lower than those produced by the TEOM. A limitation of the study was that the sensors were only tested in a chamber environment with no varying environmental conditions. The chamber experiment should be repeated seasonally to account for any sensor drift or changes from environmental factors and for a number of sources and ambient conditions.