What Ten Years of Evaluating "Low-Cost" Particulate Matter Sensors Can Tell Us About Coarse Fraction and Humidity Biases

NAMRATA SHANMUKH PANJI, Noel Ruiz, Xiaobi M. Kuang, Victor Rocha Jr., Brandon Feenstra, Wilton Mui, South Coast Air Quality Management District

     Abstract Number: 15
     Working Group: Instrumentation and Methods

Abstract
The Air Quality Sensor Performance Evaluation Center (AQ-SPEC) program at South Coast Air Quality Management District (South Coast AQMD) has evaluated the performance of over 175 "low-cost" particulate matter (PM) sensor units (comprised of over 55 sensor models) that measure both PM_2.5 and PM₁₀. While significant progress has been achieved in the affordability and accessibility of PM sensors, uncertainty remains regarding their ability to accurately detect and quantify coarse particles (PM_c = PM₁₀ – PM_2.5). Using a decade of AQ-SPEC field evaluation data, we explore the relationship between PM_2.5, PM₁₀, and PM_c readings from sensors co-located with reference monitors to identify trends, limitations, and potential mischaracterizations to understand whether sensors are able to accurately detect and quantify the coarse fraction of PM or if such readings are predominantly influenced by the fine fraction. We will explore the influence of the fine fraction on PM₁₀ and PM_c measurements along with humidity effects, which can influence particle growth and PM sensor response, further complicating the interpretation of PM measurements. These insights will help clarify the current capabilities and limitations of PM₁₀ sensors, inform sensor developers about critical areas for improvement, and illustrate the value of select performance metrics for end-users seeking to measure PM₁₀ using sensors.