Filter media of E12 filters were exposed to NaCl particles and high relative humidity. Afterwards the particle separation efficiency of DEHS (DEHS: di(2-ethylhexyl) sebacate) and pressure drop were measured according to DIN EN 1822 part 3. The results of new filter media and those at different loadings were compared to determine the influence of relative humidity or water-soluble impurities like salt. In addition, scanning electron microscope pictures were taken to achieve a better understanding of the particle behavior inside the filters. The results are compared to filter media aged in real applications.