This street cleaner, which cleans 20 miles of roadway daily, has been retrofitted with a passive diesel particulate filter (DPF). Passive DPFs reduce pollutants emitted by diesel engines and use heat from the vehicle’s exhaust to burn off the particulate matter (or soot) they collect.

This backhoe has an active diesel particulate filter (DPF) which requires an additional heat source when engine exhaust is not hot enough to burn off the trapped particulate matter (PM). Some DPFs are "regenerated" by burning a little extra fuel, while others, like this one, must be removed for cleaning.

This “cold planer” removes old road surface prior to repaving. The planer operates about 900 hours per year and uses about 6,300 gallons of fuel. The exhaust temperature was high enough for a passive diesel particulate filter (DPF) to be installed.

This equipment removes non-combustible ash build-up from all of Portland’s diesel particulate filters (DPFs). Ash build-up usually depends on how much oil an engine burns. Proper engine maintenance can help reduce the need for DPF cleaning.