Diesel particle filters
Modern diesel particle filters are in use as closed or open versions. In the closed particle filters, also known as surface filters, the exhaust gases flow through a filter unit of a porous ceramic material. While the filter gradually fills with particles, the engine managment system monitors the rise in the exhaust backpressure. Thermal regeneration of the filter takes place at an exactly defined time.
The particle oxidation catalysts, also known as open filters, have a lower separation rate (< 50%) and the filtration takes place inside a metal structure. No active regeneration is necessary for this filter type but it is unsuitable for high specific engine performances.