The present invention relates to an exhaust emission control apparatus for an internal combustion engine and a process for operating it. The exhaust emission control has a particulate filter for filtering particulate matter from the exhaust of the internal combustion engine, at least one temperature sensor for detecting the temperature of the exhaust, an evaluation unit for evaluating the detected temperature, particularly with regard to a particulate mass burned during a regeneration operation of the particulate filter. The temperature sensor is positioned inside the particulate filter.