U.S. Department of Energy - Energy Efficiency and Renewable Energy
Vehicle Technologies Office
Fact #502: January 21, 2008
Off-Road Diesel Equipment Facing Tougher Emissions Regulation
The Environmental Protection Agency began regulating off-road diesel emissions in 2000 with the phase in of Tiers 1-3, which only applied to diesel engines above 50 horsepower. Beginning in January 2008, Tier 4 regulations will include all diesel engines and will in some cases reduce nitrogen oxide and particulate matter limits to levels similar to current on-road diesel engines. Tier 4 regulations will be phased in over a seven year period beginning with the smallest engines and gradually including larger off-road diesel equipment.
Tier 4 Off-Highway Diesel Emission Standards
(grams per horsepower-hour)
|Less than 25
|25 to 74
|75 to 174
|175 to 749
PM: Particulate Matter
NOx: Nitrogen Oxides
* The 0.50/g/hp-hr applies to generator sets more than 1200 hp.
** The 0.02/g/hp-hr applies to generator sets; the 0.03 g/hp-hr applies to other engines.
*** Applies to all generator sets only.
- Not regulated
Source: U.S. Environmental Protection Agency.
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