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This study used a parallel-plate wet denuder coupled with an ion chromatograph (PPWD-IC) to monitor soluble gas pollutants in the exhaust stack and investigate the removal efficiency of packed towers. Gas pollutant concentrations measured by the PPWD-IC system were first validated with those obtained by a manual porous metal denuder sampler (PDS) as the reference sampler. The measured concentrations of the PPWD-IC system are in good agreement with those of the PDS with the coefficient of determination (R2) greater than 0.93. The PPWD-IC system was then used to determine the removal efficiency of packed towers in high-tech factories. Results show that the PPWD-IC system is able to monitor multiple high-concentration gas pollutants semi-continuously, such as HF, HCl, HNO2, HNO3, CH3COOH, and NH3, in the exhaust stack with a temporal resolution of 20 min. The PPWD-IC system was employed to test the gas removal efficiency of a new honeycomb wet scrubber in an optoelectronic factory. The removal efficiency of the wet scrubber equipped with the honeycomb module at the liquid-to-gas ratio of 18.5 L/m3 is shown to be close to 100% for HF (112.4–448.4 ppbv) and CH3COOH (696.3–6537.0 ppbv) and 99% for HCl (3394.9–10794.5 ppbv), respectively.