A Field Assessment of the InterScan 4240 SO_2 Analyzer and the Thermo 43C SO_2 Analyzer

摘要

Operating the InterScan 4240 alongside the Thermo 43C provided a unique opportunity to evaluate the performance characteristics of the InterScan 4240, a lower-cost sensor. While every measurement system has the potential for measurement error, given that the Thermo 43C is an accepted EPA-equivalent method analyzer for SO_2, and given that this analyzer passed routine QA/QC checks, it is assumed that the significant differences in measurement results between the two systems are primarily due to measurement error associated with the InterScan 4240. Assuming the validity of measurement data generated by the EPA designated FEM Thermo 43C, the largest issue encountered with the InterScan 4240 in the study was its tendency to respond to gases in the local environment aside from SO_2. Future studies could challenge the instrument with a variety of suspected interferrents over a range of concentrations to evaluate their impact on instrument response. It is important for data users to know and understand the limitations of ambient air monitoring data collected from electrochemical sensors. Limitations that significantly influence data quality include baseline drift, analyzer sensitivity, and the potential for the analyzer to respond to other compounds in the air. If similar air monitoring sensors are used by the general public, these potential limitations need to be well understood and explained.