The atmosheric pressure piasma treaments of activated carbon fibers were carried out to introduce hydrophilic functional groups on carbon surfaces in order to enhance the hydrogen chloride gas adsorption. Surface preperties of the ACFs were determined by XPS and SEM. N₂/77 K adsorption isotherms were investigated by BET and D-R plot methods. The HCL remival efficiency was confirmed by HCl detecting tubes(range: 1~4 or 40~1000 ppm).