Tenneco Inc. will introduce the first line of replacement Diesel Particulate Filters (DPF) and Diesel Oxidation Catalysts (DOC) through its Walker exhaust brand. DPF and DOC products have been used in light-and medium-duty diesel trucks, SUVs, and full-size vans since the 2007 model year, when the U.S. Environmental Protection Agency reduced allowable emissions of nitrogen oxide (NOx) and hydrocarbons (HC) by 50% and particulate matter by more than 90%. Usually mounted downstream of the DOC, a DPF features a precisely engineered honeycomb structure that traps microscopic particulates within the exhaust stream. A DOC works much like a conventional catalytic converter in creating a chemical reaction that helps clean combustion gases. New Walker DPF and DOC units will be available early next year for the following applications: 2008-09 6.4-litre Ford F250, F350 Super Duty; 2007-08 6.7-litre Dodge Ram 2500, 3500; and 2007-08 6.6-litre Chevrolet Silverado and GMC Sierra 2500.