When is a particulate filter required?

The EU emission standards (Regulation (EC) No 715/2007) limit not only the particulate mass but, since Euro 5b/6, also the particle number. On diesel engines these limit values can in practice only be met with a diesel particulate filter (DPF).

With Euro 6, the particle-number limit was extended to direct-injection petrol engines; these generally require a petrol particulate filter (OPF). A particulate filter is therefore not a mandatory component in itself, but a consequence of the emission limit values to be met.

Removing or tampering with a factory-fitted particulate filter is unlawful — the vehicle then no longer meets the approved emission standard.