Donaldson Co.'s Diesel Oxidation Catalyst (DOC) muffler and Spiracle crankcase ventilation filter has been approved by the Environmental Protection Agency for retrofitting to diesel engines built since 1991.

Minneapolis-based Donaldson said its DOC muffler and crankcase filter combination can cut diesel engine emissions from medium- and heavy-duty trucks as well as school buses by 25% to 50%.

Steve Schmeichel, Donaldson's emissions manager, added that up to 25% of the pollution generated by a diesel-powered vehicle comes from the crankcase. That's why tailpipe-only emission control systems ignore what he calls “a big contributor” to the pollution problem posed by diesel engines.