Combining Donaldson's DOC Muffler and the Spiracle Crankcase Vent Filtration System will reduce particulate matter emissions from medium- and heavy-duty diesel trucks by more than 25 percent. The system received Level 1 Verification from the California Air Resources Board, which enables Donaldson to sell the combination as a retrofit to help California vehicle operators meet state pollution restrictions. Donaldson is also the first company in the nation to be approved by the U.S. EPA's Environmental Technology Verification Program. The muffler is a direct replacement for most OEM mufflers and uses a diesel oxidation catalyst to remove 15 to 30 percent of particulate matter. The Spiracle filters eliminate 100 percent of crankcase-vent emissions and keep the engine compartment clean. The system fits a broad range of engines manufactured since 1991. Estimated list price: $1,500 to $2,000.