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March 01, 2006  |   Comments (0)   |   Post a comment

Fleet Facts About Diesel Particulate Filters

What you need to know about these emission-control devices, which are being retrofitted into thousands of school buses and will be installed in all 2007 diesel models.

by Steve Hirano, Editor

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“So far, it’s been fantastic,” Beaubien says. The difference in the amount of smoke produced by the buses has been significant. “Now it’s like they’re not even running,” he says.

The only significant change in the transportation department’s operations is the implementation of an anti-idling policy. Beaubien says drivers are warned against idling too long because of the possible build-up of soot in the DPF.

DPF manufacturer list
The following are some of the diesel particulate filter products available:

The DPF Muffler removes over 85 percent of particulate matter and meets the EPA’s Voluntary Retrofit Program and the California Air Resources Board’s Risk Reduction Program. The device is available for most exhaust configurations in bus models 1994 and newer. Under normal operation, the filter requires cleaning annually or every 50,000 miles, whichever comes first. An onboard filter service (backpressure) monitor is included with each DPF. The device requires the use of ULSD. Donaldson also manufactures two cleaning systems — a pulse cleaner and a thermal regenerator. For more information, visit

The DPX particulate filter traps particles and then uses a patented catalytic technology to continuously burn them at normal diesel operating exhaust temperatures. The filter reduces particulate matter by 90 percent, soluble organic fractions by 98 percent and carbon monoxide and hydrocarbons by up to 90 percent. It does not require low sulfur diesel fuel or additives. For more information, visit

The DPF uses EPA-verified Continuously Regenerating Technology (CRT) that removes up to 85 percent of particulate matter emissions. The next-generation Catalyzed Continuously Regenerating Technology (CCRT) retrofit system works for lower-temperature applications. To ensure optimum performance of the filter and engine, the DPF system monitors engine pressure and temperature. Controls in the driver’s compartment alert the driver when backpressure is high and the filter needs cleaning. The CRT and CCRT systems achieve maximum emission reduction with ULSD and are verified for use with biodiesel (up to B20 with ULSD). For more information, visit

International’s diesel particulate filters use Engelhard technology to provide a 70 to 98 percent reduction in particulate matter and visible smoke, depending on fuel quality, and a 70 to 98 percent reduction in carbon monoxide and hydrocarbons. ULSD should be used with this filter, but occasional use of higher sulfur fuel in emergency situations will not damage the system or stop the vehicle. International recommends cleaning and visual inspection at least once every 12 months or every 60,000 miles. The system includes a pressure monitor sensor that will indicate the need for cleaning. The filter is available for use on most diesel buses and medium trucks with electronic engines. For more information, visit

The CRT particulate filter uses a patented process to oxidize soot in the presence of NOx at a lower temperature than with oxygen. This lower temperature is compatible with typical diesel exhaust temperatures, so no supplemental heat is required. The filter reduces the emission of hydrocarbons, carbon monoxide and particulate matter by more than 90 percent. For more information, visit

The Smoke Blotter system consists of a filter, housing, diverter, actuator and control module. These self-contained units effectively trap 95 to 99 percent of soot. The system can be connected to a patented “Phantom Switch.” This switch turns on the filter when the vehicle enters a predefined radius of low-frequency transponders that can be strategically placed near schools, bus stops and other places where people congregate. This prolongs the service life of the system. For more information, visit

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