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Next Generation Air Monitoring (NGAM) VOC Sensor Evaluation Report
Citation:
Williams, R., A. Kaufman, AND S. Garvey. Next Generation Air Monitoring (NGAM) VOC Sensor Evaluation Report. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-15/122 (NTIS PB2015-105133), 2015.
Impact/Purpose:
The National Exposure Research Laboratory’s (NERL’s) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA’s mission to protect human health and the environment. HEASD’s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA’s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
This report summarizes the results of next generation air monitor (NGAM) volatile organic compound (VOC) evaluations performed using both laboratory as well as field scale settings. These evaluations focused on challenging lower cost (<$2500) NGAM technologies to either controlled or ambient conditions. The cost ceiling applied to the technologies selected for evaluation reflected a value believed to be the limit to what citizen scientists might seek to obtain for their use. The work conducted here and the summary of findings is not meant to be a definitive description of all such technologies. It represents a first step in understanding the capabilities of lower cost VOC technologies and their limitations. An exhaustive search of commercially-available VOC NGAM products under the $2500 limit yielded a very modest number of devices available for inclusion in the research. Ultimately a total of five (5) devices were incorporated into the evaluation with one of those being an EPA developed device which used a commercially-available VOC photoionization detector (PID) as the sensing element.The laboratory evaluations involved challenging the devices to a stepwise pattern of VOC concentrations at levels believed to be environmentally relevant (< 25 ppb) using a chamber. Reference gas chromatographic (GC) detection was utilized to verify the challenge conditions being established. The devices were first evaluated for their response to a single VOC (benzene). If the device revealed some ability to detect benzene at even 25 ppb it was then challenged with an atmosphere consisting of three VOCs (benzene, 1,3-butadiene, and tetrachloroethylene). These compounds were selected because of the availability of well qualified test gases and the fact they represented a variety of VOC moieties (structural variability). The response of the devices to the various challenge conditions are reported. NGAM devices were deployed at an outdoor near road test platform for an extended period where wide variability of VOC conditions were expected to exist. The research plan involved direct comparison of the NGAM response to GC reference data from collocated measurements obtained at the test site. Reference data were ultimately not available for the intended comparisons (instrument malfunction and insufficient resources to conduct a timely repair). Therefore, field data provided here are limited to non-reference comparisons between NGAM devices. Such comparisons, providing a non-quantitative assessment of true VOC response still have the potential of yielding useful information on the relative response characteristics of the NGAM VOC devices evaluated.