DIWS system was introduced to treat HCl gas from the scrubber of iron and steel industry according as the regulationof air quality is expected to be changed to 2ppm. pH of condensed water at stack was increased to 6.0. While13.3ppm of inflow HCl was introduced to DIWS system, the average exhaust gas was 0.43ppm with 96.9% ofremoval efficiency. Compared with HCl data of TMS, the stable removal efficiency was shown in DIWS system, butthe phenomenon of data hunting was also observed with different types of TMS apparatus.