Performance of automated ambient SO2 analyzers with respect to a proposed 5-minute ambient air-quality standard

The U. S. Environmental Protection Agency is considering an additional ambient air quality standard for SO2 that would be based on average SO2 concentration over a 5-minute period. The paper investigates the speed-of-response characteristics of currently used SO2 continuous monitoring instruments and their adequacy for monitoring 5-minute averages. Two analyzers were laboratory-tested to determine their time-response characteristics. Mathematical models of instrument performance were then developed to study measurement accuracy for various short-duration SO2 concentration pulses. These brief experiments indicated that the response of the analyzers tested, which meet the current reference and equivalent method response specifications, was not adequate for monitoring 5 minute averages accurately