DPF Blocking and Particulate Matter

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Particulate Matter and Blocking

Diesel Particulate Filters are designed to trap the Particulate Matter (PM) that is produced by diesel engines. PM is a complex mixture of small particles and droplets which primarily consist of soot and ash.


Soot consists of small particles of carbon which are trapped by the DPF. Using a process known as regeneration we can burn off these carbon deposits allowing normal flow to be restored to the filter. Many vehicles are already fitted with regeneration systems that operate without needing any additional attention from the driver. However, vehicles that drive around busy urban areas and need to stop and start a lot more don’t regenerate their DPF’s as effectively. This can then lead to premature soot blockages.


Ash, like soot, is a by-product of diesel engines, however, it can’t be cleaned by the regeneration processes or chemical cleaners added to the fuel. As a result, the DPF’s need regular cleaning to keep them and the engine operating efficiently.

Blocked DPFs

When a filter is clogged it can experience an increase in exhaust back pressure. With most vehicles, a warming light will alert the driver that this is happening and the DPF needs cleaning. However, other clues that the filter may be blocked are a significant deterioration in engine performance and increase fuel consumption. Severe cases can result in permanent damage. Where the exhaust gas flow has become extremely restricted the filter can become cracked or burnt-out.