Johnson Matthey has gained US EPA verification for its CCRT diesel particulate filter system, dieselnet.com has reported.

The system is now eligible for use in the EPA's Voluntary Diesel Retrofit Program (VDRP) and other such programmes in the US.

This verification is an extension of the CRT filter verification. Both the CRT and CCRT filters generate SIP emission credits of 60 per cent for PM, CO, and HC.

JM's CRT (Continuously Regenerating Trap) filter system incorporates an oxidation catalyst positioned upstream of an uncatalyzed particulate filter, which is regenerated using nitrogen dioxide generated in the catalyst.

The CCRT configuration (Catalyzed CRT) includes an upstream catalyst and a catalyzed particulate filter, combining the regeneration mechanisms found in the CRT filter and in catalyzed filters.

Johnson Matthey said the CCRT has been successfully operating in school buses in California and Massachusetts, and other applications that are too cold for the CRT filter.