Effect of Nafion Dryer and Cooler on Ambient Air Pollutant (O3, SO2, CO) Measurement

Water vapor causes many problems in ambient air measurement by absorbing target compounds concerned. In accordance with Korean national standards and international organization for standardization (ISO), water removal devices (WRDs) such as Nafion dryer and Cooler have been applied to analyzers to mitigate or remove the effect of water vapor on the measurement of ambient air pollutants. However, it is not clearly defined which WRDs are suitable for the measurement. Thus, Roll type Nafion dryer (RN), Mono type Nafion dryer (MN), and Cooler (CL) were investigated to figure out their water removal efficiencies and their effect on target compounds. Ozone (O-3), sulfur dioxide (SO2), and carbon monoxide (CO) were used as target compounds in this study. Concentrations of O-3, SO2, and CO were 100 ppb, 150 ppb, and 25 ppm, respectively. All experiments were conducted at 25 degrees C and 1 atm. Water vapor was varied as 0, 30, 50, and 80% of relative humidity (RH). In general, 10% decrements of O-3 and SO2 with respect to relative humidity were clearly observed. In terms of a recovery, all WRDs revealed significant effect on O-3 and SO2 recovery. Additionally, water removal of RN was the highest followed by MN and Cooler. Consequently, it was suggested that WRDs should be taken into account according to the chemical and physical specifications of ambient air pollutants of concern.