<;P>;PROBLEM TO BE SOLVED: To develop innovative air cleaning technology highly efficiently and completely removing harmful gas components despite a small-size device, treating a massive amount of air and having an adsorbent material with little functional decline. <;P>;SOLUTION: This is the usage of an activated carbon fiber sheet that removes the volatile organic compounds in the air by non-filtering method using the activated carbon fiber sheet as a ventilation passage constituent material of a diffusion scrubber which passes gas through a clearance constituting a ventilation passage, selectively adsorbs the gas on the ventilation passage surface using a difference in a diffusion coefficient between gas and particles contained in the gas and removes them from the gas. This method is applied to an air cleaner as the structure obtaining the harmful gas removal efficiency of 50% or more in a single pass in a theoretical formula expressing the principle of the diffusion scrubber of Gormley and Kennedy. <;P>;COPYRIGHT: (C)2007,JPO&INPIT