Obviously if DPM is allowed to collect in the filter, and not somehow removed, the filter will become blocked. The process of removing the DPM is known as regeneration. To regenerate the filter, it is necessary to burn the DPM, but the fundamental problem is that DPM will not burn unaided until it reaches a temperature of at least 550 C, which is rarely available in a Diesel exhaust. There are two main approaches to getting over this problem, which can be classified as 'passive' or 'active'.
