Due to the low bulk density of diesel particulates, which is typically below 0.1 g/cm3 (the density depends on the degree of compactness; as an example, a number of 0.056 g/cm3 was reported by Wade [Wade 1981]), diesel particulate filters can quickly accumulate considerable volumes of soot. Several litres of soot per day may be collected from an older generation heavy-duty truck or bus engine. The collected particulates would eventually cause excessively high exhaust gas pressure drop in the filter, which would negatively affect the engine operation. Therefore, diesel particulate filter systems have to provide a way of removing particulates from the filter to restore its soot collection capacity. This removal of particulates, known as the filter regeneration, can be performed either continuously, during regular operation of the filter, or periodically, after a pre-determined quantity of soot has been accumulated, in either case, the regeneration, which clean the blocked-up filter should be “invisible” to the vehicle driver/operator and should be performed without his intervention.