Periodically regenerable cake-forming surface filters are widely used in particulate control technology. The particles collected on the filter medium surface build up a so-called ＇dust cake＇. The operational characteristics of such filter apparatus are strongly influenced by the structure of the dust cake formed. The structure itself depends (among other factors) on the particle size distribution, particle charge, adhesive and cohesive properties, and on the pressure drop. The dust cake mass and therefore its flow resistance with respect to pressure drop increase with filtration time. This rise in pressure drop is in many cases not linear. Local compressions of the dust cake are considered to be responsible for the progressive increase of pressure loss with time. This theory was confirmed by quantitative analyses of dust cake structures in an earlier paper. The present paper reports on a simulation program based on a simple model, by which local transient porosities inside the dust cake and the pressure drop as a function of time can be calculated.