When different cleanable filter media are tested according to the VDI 3926 guideline, the aging procedure influences the test result. A new simple aging chamber was developed within the scope of this work, by which long term aging tests can be carried out without blocking the technical sophisticated VDI 3926 test equipment. During the investigation of the aging progression it turned out that after a certain aging time the pressure drop over the filter media shows an extreme increase. This effect has been investigated in detail and the reason was found in the steady increasing under pressure on the clean gas side and the corresponding over pressure decrease during the regeneration. Compared to the well known pressure controlled cleaning the steady under pressure increase is the major cause for the observed differences in the filtration mechanisms. The extreme pressure drop increase occurs for shorter cycle times, slower filtration velocities and higher cleaning intensities later and will most probably not be observed with the usual VDI aging test conditions (short cycle times, slow filtration velocity). It will be proposed to use the time of the extreme pressure drop increase as a characteristic aging value for the estimation of the clogging behaviour. As an additional method for evaluating the filtration behaviour of different filter media the characteristic aging value is used in combination with the mean clean gas concentration and the residual dust mass. The significance of the comparison of different filter media is improved by plotting these specific values over the filtration velocity. (C) 2010 Elsevier B.V. All rights reserved.