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Sensor evaluations: The impact of PM2.5 monitor type
Citation:
Barkjohn, K., A. Clements, A. Holder, R. Vanderpool, T. Hanley, AND B. Gantt. Sensor evaluations: The impact of PM2.5 monitor type. National Ambient Air Monitoring Conference, Pittsburgh, PA, August 22 - 25, 2022.
Impact/Purpose:
Air sensors have grown in popularity in recent years. They have the potential to provide more spatially dense measurement than conventional monitors. However, to gather accurate data, co-location and comparison with conventional air monitors are often needed. The monitor type selected can impact perceived performance. This work will be presented at the National Ambient Air Monitoring conference August 22-25, 2022 in Pittsburgh, PA.
Description:
PM2.5 sensors are typically collocated with conventional air monitors to better understand their performance. These monitors may include federal reference methods (FRM), federal equivalent methods (FEM), temporary smoke monitors, research-grade methods, or other near FEM technology. This work evaluates the strengths and limitations of these comparison measurements and the implications for correctly interpreting sensor evaluation results. This work uses PurpleAir sensors collocated with a variety of monitors across the U.S. to explore the influence of comparison monitor type on perceived sensor performance. In addition, the bias of Teledyne T640 and T640x monitors has been evaluated to understand when these monitors are most suitable for sensor comparisons. The Teledyne T640 and T640x have become popular FEM choices in the past few years, and they make an excellent comparison for many low concentration sites across the U.S. due to their high precision at low concentrations. This work analyzes 3 years of collocated T640 and FRM data from across the U.S. to understand T640/T640x bias. Piecewise regression was used to understand nonlinearity at higher concentration. Findings suggest that T640 data may have a nonlinear relationship with FRM concentrations above ~35 µg/m3. Understanding the strengths and limitations of monitors is crucial when using them to evaluate air sensors.