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Field and Laboratory Performance Evaluation of an Ozone Sensor
Williams, R., D. Vallano, R. Duvall, A. Polidori, B. Feenstra, H. Zhang, AND V. Papapostolou. Field and Laboratory Performance Evaluation of an Ozone Sensor. 2018 Air Sensors International Conference, Oakland, CA, September 12 - 14, 2018.
Presentation at the 2018 Air Sensors International Conference.
The Air Quality Sensor Performance Evaluation Center (AQ-SPEC) at the South Coast Air Quality Management District (SCAQMD) US EPA recently completed a laboratory and field evaluation of the U.S. EPA’s Citizen Science Air Monitor (CSAM) sensor pod. The CSAM is a multi-pollutant instrument package capable of continuous measurement of ozone, particulate matter, temperature, and relative humidity under ambient monitoring conditions. Ten identical units of the CSAM were involved in the evaluation. Performance testing of the CSAM’s electrochemical-based ozone sensor (Aeroqual SM-50) under both field and laboratory conditions was conducted with collocated federal equivalent method (FEM) instruments. Ambient test conditions were associated with the field-based evaluations at the Riverside-Rubidoux regulatory monitoring site in California while a controlled laboratory testing environment (relative humidity, temperature, target and interferent pollutant concentrations) provided data to assess a variety of the ozone sensor’s performance characteristics. Field-based results (5-min comparisons) showed excellent correlation with the FEM (R2 > 0.83) with some underreporting of the concentration (10 to 50%) dependent by individual CSAMs. Two CSAM units were selected for extensive laboratory evaluation and yielded excellent correlation with in-line FEM instrumentation (R2 > 0.95) but with significantly reduced response over test conditions of 0 to 310 ppb (accuracy ranging from ~ 18 to 86%). Select conditions of low temperature (5 oC) revealed spurious sensor response while the sensor exhibited minimal response to nitrogen dioxide challenges up to 250 ppb. Features of the CSAM along with test conditions and other features of the evaluations will be presented. The merit of field versus laboratory-based sensor evaluations shall be discussed.