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We have investigated the cross-sensitivity of a commercially available SO 2 monitor (TEI 43 C-FG) with respect to the fluorescence of NO, CO and CO 2. Quenching of the NO and the SO 2 fluorescence by O 2 and CO 2 was also determined. The results were implemented in a set of equations and subsequently used to correct the monitor's output for possible interferences. For highly variable O 2 concentrations, quenching by molecular oxygen was controlled by dilution of the sample gas with synthetic air. The response of an UV-fluorescence monitor to various gases is largely determined by the light spectrum used for excitation and detection. Therefore, absorption spectra of the main components were measured. Furthermore, fluorescence spectra of SO 2 and NO were obtained as a function of the excitation wavelength. Based on these data, the advantages and limitations inherent to the selection of filters are discussed and further improvements suggested.

Water vapor is a pivotal obstacle when measuring ambient air pollutants. The effects of water vapor removal devices which are called KPASS (Key-compound PASSer) and Cooler. On the measurement of O3, SO2, and CO at ambient levels were investigated. Concentrations of O3, SO2, and CO were 100 ppb, 150 ppb, and 25 ppm, respectively. The amount of water vapor varied at different relative humidity levels of 30%, 50%, and 80% when the temperature was 25 °C and the pressure was 1 atm. Water vapor removal efficiencies and recovery rates of target gases were also determined. The KPASS showed a better performance than the Cooler device, removing 93.6% of water vapor and the Cooler removing 59.2%. In terms of recovery, the KPASS showed a better recovery of target gases than the Cooler. Consequently, it is suggested that the KPASS should be an alternative way to remove water vapor when measuring O3, SO2, and CO.

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