During the process of filtration, filtration efficiency E as well as pressure loss delta p change so that the overall process is not stationary. As soon as the filter structure is covered with a layer of deposited aerosols, the fibre diameter increases and thus the packing density coefficient, i.e. the permeability of the system for the dispersion medium is reduced. This causes a disadvantageous rise of the pressure loss. At the same time, however, separation efficiency increases with the reduction in the open crosssection area, as now also particles with smaller diameters will be retained.
