A Diesel Particulate Filter, also know as a DPF Filter is a device that is fitted to remove soot from exhaust gasses.
Diesel Engines produce a variety of particles during combustion of the fuel/air mix due to incomplete combustion. The composition of the particles varies widely dependent on different things like engine type, age, and the emissions specification that the engine was designed to meet.
DPF Filters require more maintenance than catalytic converters. Ash, a byproduct of oil consumption from normal engine operation, builds up in the filter as it cannot be converted into a gas and pass through the walls of the filter. This increases the pressure before the filter. Warnings are given to the driver before filter restriction causes an issue with drive-ability or damage to the engine or filter develop. Regular filter maintenance is a necessity.
DPF filters go through a regeneration process which removes this soot and lowers the filter pressure. There are three types of regeneration: active, passive, and forced. Active regeneration happens while the vehicle is not in use and takes 10 minutes on average to complete. Passive regeneration takes place while driving using the heat of the exhaust. This works well for vehicles that drive longer distances with few stops compared to those that perform short trips with many starts and stops. If the filter develops too much pressure then the last type of regeneration must be used – a forced regeneration. This involves a garage using a computer program to run the car, initiating a regeneration of the DPF manually.