Fractures of rigid ceramic filters hinder the long-term stable operation of high-efficiency power generation plants. In this paper, we focused on thermal stress fractures due to char combustion in collected ash layers on the ceramic filter surface. By using a bench scale dust collector model system with a ceramic filter, the temperature profiles on the filter surface during char combustion were directly measured. When the carbon content of the ash layer was about 16 wt.%, the maximum temperature difference between the inside and outside surfaces of the filter reached 500 K. Based on this result for the temperature profile, the maximum thermal stress of cylindrical, ceramic filter elements prepared from various materials was predicted. Since the estimated thermal stress exceeded the fracture strength of some kinds of porous materials, it is concluded that thermal stress fracture due to char combustion on filter surfaces is one of the important fracture mechanisms of rigid ceramic filters.