Ultrafine dust separation from different sources like industry, traffic, or private households has become increasingly important in the last decade. A compact baghouse filter system has been developed which is suitable for pellet heaters. For filtration, a precoat material is required to prevent clogging of the filter media by the ultrafine dust particles. In order to ensure the best performance of this filter system, different combinations of filter media and precoat materials, e.g., grade efficiencies and the cake area load for the various filter media, were investigated in a special test rig. With this highly efficient technology, extremely high separation efficiencies of >99% and ultrafine dust concentrations of >1mgcm-3 could be reached in a long-term stable process.