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About retrofit devices
The EPA defines a retrofit device as any device that reduces emissions below the levels required by law.
Most diesel retrofit devices are similar in appearance to the mufflers they replace. Using catalytic processes and/or filter technology, they reduce carbon monoxide, hydrocarbon emissions and particulate emissions.
- Technologies that reduce diesel exhaust in the outside air:
- Diesel oxidation catalyst (DOCs): DOC’s are devices that reduce PM emissions by 30% to 40%. Many 2005 buses have DOCs already installed on the original equipment.
- Diesel multistage filters (DMFs): DMF’s are a newer flow-though catalytic technology that reduces PM emissions by 50-70%.
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Reduce exhaust emissions inside the bus:
- Internal Closed Crankcase ventilation Filters (CCVs): CCVs eliminate emissions from the engine crankcase which is estimated to be about 10 percent of the total bus emissions. This technology is very important because it reduces emissions inside the cab of the bus where students and drivers face the highest PM exposure.
New 2007 model year, heavy-duty engines meet lower emission levels and do not need retrofitting.
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ADDITIONAL RESOURCES:Funding:
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