List of Formerly Verified Technologies for Clean Diesel

Air Pollutants

The list below provides information about diesel retrofit technologies that EPA formerly approved or conditionally approved, but that are no longer on that list.

It also shows the percent reduction that EPA would have recognized for emission reductions from each technology.

On this page:

Formerly Verified Retrofit Technologies

Manufacturer Technology Applicability       Percent Reduction
PM NOx HC CO
Cummins Emission Solutions Cummins Emission Solutions & Cummins Filtration Diesel Oxidation Catalyst (DOC) and Closed Crankcase Ventilation (CCV) System Highway, heavy-heavy and medium-heavy duty, 4 cycle, non-EGR, model year 1991 - 2003, turbocharged or naturally aspirated engines 30 n/a 74 50
Engine Control Systems Limited AZ Purimuffler or AZ Purifier Diesel Oxidation Catalyst (DOC) with ECS Closed Crankcase Ventilation (CCV) system with Low Sulfur Diesel Fuel (LSD) Highway, heavy heavy-duty, 4-cycle, mechanically or electronically injected, turbocharged or naturally aspirated, originally manufactured from 1991 through 2004 model years which meet a 5 or 4 g/bhp-hr NOx standard with open crankcase ventilation and no after treatment engines 40 n/a 75 60
Engine Control Systems Limited AZ Purimuffler Diesel Oxidation Catalyst (DOC) with Low Sulfur Diesel Fuel (LSD) Highway, medium heavy-duty, 4-cycle, model years 1991 - 2003 Cummins and Navistar/International engines originally manufactured with no after treatment, turbocharged or naturally aspirated, non-EGR engines 40 n/a 70 40
Engine Control Systems Limited AZ Purimuffler or AZ Purifier Diesel Oxidation Catalyst (DOC) with Low Sulfur Diesel Fuel (LSD) Highway, heavy heavy-duty, 4-cycle, model years 1991 - 1993 Cummins engines originally manufactured without exhaust after treatment, turbocharged or naturally aspirated, non-EGR engines 35 n/a 70 40
Engine Control Systems Limited AZ Purimuffler AZ Purifier Highway, heavy duty, 2-cycle engines 20 n/a 50 40
Engine Control Systems Limited AZ Purimuffler AZ Purifier Highway, heavy duty, 4-cycle engines 20 n/a 50 40
International Truck & Engine Corp. Green Diesel Technology-Low NOx Calibration plus Diesel Oxidation Catalyst (DOC) with Ultra Low Sulfur Diesel (ULSD) Highway, light heavy-duty, 4-cycle, Navistar/International engines, model years 1999 - 2003 in the following families:
XNVXH0444ANA, YNVXH0444ANB, 1NVXH0444ANB, 2NVXH0444ANB, 3NVXH0444ANB		 0 to 10 25 50 10 to 20
Lubrizol PuriNOx Water emulsion fuel Highway & Nonroad, heavy-duty, 2 & 4-cycle 16 to 58 9 to 20 -30 to -120 -35 to 33

Formerly Conditionally Verified Retrofit Technologies that Did Not Fulfill Necessary Conditions for Verification

Manufacturer Technology Applicability Percent Reduction
PM NOx HC CO
Engine Control Systems Limited AZM Purimuffler or AZM Purifier Diesel Oxidation Catalyst (DOC) Highway, heavy-duty, 4 cycle engines 1991 through 2006 20 n/a 50 40
Engine Control Systems Limited AZM Purimuffler or AZM Purifier Diesel Oxidation Catalyst (DOC) with ECS Closed Crankcase Ventilation (CCV) System Highway, heavy-duty, 4-cycle, mechanically or electronically injected, turbocharged or naturally aspirated, originally manufactured from 1991 through 2006 model years which meet a 5 or 4 g/bhp-hr NOx standard. 25 n/a 50 40
Engine Control Systems Limited Purifilter Plus (Diesel particulate filter on the engine, electrical panel for active regeneration at the garage/maintenance yard) Highway; heavy, medium, and light heavy-duty; Urban Bus; 4-cycle; model years 1994 - 2006; turbocharged or naturally aspirated; EGR engines 90 n/a 85 75

Formerly Verified Retrofit Technologies that Do Not Comply with the 2009 NO2 Limits

Manufacturer Technology Applicability Percent Reduction
PM NOx HC CO
Caterpillar, Inc. Catalyzed Converter/Muffler (CCM) Highway, heavy-heavy and medium-heavy duty, 4 cycle, non-EGR, model year 1998 - 2003, turbocharged or naturally aspirated engines 20 n/a 40 20
Clean Diesel Technologies, Inc. Platinum Plus Purifier System
(fuel borne catalyst plus DOC)		 Highway, medium heavy- and heavy heavy-duty, 4 cycle, model year 1988 - 2003, turbocharged or naturally aspirated engines 25 to 50 0 to 5 40 to 50 16 to 50
Clean Diesel Technologies, Inc. Platinum Plus Fuel Borne Catalyst/Catalyzed Wire Mesh Filter (FBC/CWMF) System Highway, medium heavy-duty, 4 cycle, model year 1991 - 2003, non-EGR, turbocharged or naturally aspirated engines 55 to 76 0 to 9 75 to 89 50 to 66
Engelhard DPX Catalyzed Diesel Particulate Filter Highway, heavy-duty, 4 cycle, model year 1994 - 2002, turbocharged or naturally aspirated engines 60 n/a 60 60
Engelhard CMX Catalyst Muffler Highway, heavy-duty, 2 cycle engines 20 n/a 50 40
Johnson Matthey Partial Continuously Regenerating Technology2 (PCRT2) Particulate Filter Highway, heavy-heavy and medium-heavy duty, 4 cycle, non-EGR, model year 1988 - 2003, turbocharged or naturally aspirated non-urban bus engines 50
(MY1988-1993)
45
(MY1994-2003)		 n/a 92 68
Johnson Matthey Catalyzed Continuously Regenerating Technology (CCRT) Particulate Filter Highway, heavy-duty, urban bus, 4 cycle, non-EGR model year 1994 - 2006, turbocharged or naturally aspirated engines. 90 n/a 95 85
Johnson Matthey Continuously Regenerating Technology (CRT) Particulate Filter Highway, heavy-duty, 4 cycle, model year 1994 - 2006, turbocharged or naturally aspirated engines 90 n/a 95 85
Johnson Matthey CEM Catalyst Muffler Highway, heavy-duty, 2 cycle engines 20 n/a 50 40
Paceco Corporation MES diesel particulate filter (MES-DPF) Pre-1996 nonroad, 4-cycle, heavy-duty diesel engines in the 225 - 450 kW (NR7) power range in electrical generation applications 39 n/a 95 90
PUREM PMF Green-Tec Particulate Filter/Catalyst Highway, medium-heavy duty up to 280 hp, 4 cycle, non-EGR, model year 1998 - 2003, turbocharged or naturally aspirated engines 90 n/a 90 85
PUREM PMF Green-Tec 230 Particulate Filter/Catalyst Highway, medium-heavy duty up to 230 hp, 4 cycle, non-EGR, model year 1998 - 2003, turbocharged or naturally aspirated engines 90 n/a 95 80
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Last updated on April 28, 2025