Environmental Protection Agency (EPA)

EPA's Office of Transportation and Air Quality protects public health and the environment by regulating air pollution from motor vehicles, engines, and the fuels used to operate them, and by encouraging travel choices that minimize emissions. These "mobile sources" include cars and light trucks, heavy trucks and buses, nonroad engines, equipment, and vehicles.


Forklifts, Generators, and Compressors (gasoline/propane)

This page provides regulations and guidance documents for nonroad spark-ignition (SI) engines over 19 kW (25 horsepower), including many kinds of equipment, such as forklifts, generators, and many other farm, industrial and construction applications. These engines may operate on propane, gasoline, or natural gas.


Heavy Trucks, Buses and Engines

This page presents emission-related information about heavy-duty highway engines, such as those used in trucks and buses. Much of this content is focused on diesel engines, but requirements also apply for gasoline-fueled and other spark-ignition engines. The requirements apply to engines installed in all vehicles with Gross Vehicle Weight Rating above 14,000 pounds, and to some engines installed in vehicles with Gross Vehicle Weight Rating between 8,500 and 14,000 pounds.


Lawn and Garden (Small Gasoline) Equipment

EPA has adopted emission standards to control both exhaust and evaporative emissions from small spark-ignition engines. Phase 3 exhaust emissions standards take effect in 2011 or 2012, depending on the size of the engine. Evaporative emission standards address fuel permeation through fuel-system components in addition to fuel venting during engine operation.



In March 2008, EPA finalized a three part program that will dramatically reduce emissions from diesel locomotives of all types -- line-haul, switch, and passenger rail. The rule will cut PM emissions from these engines by as much as 90 percent and NOx emissions by as much as 80 percent when fully implemented. The standards are based on the application of high-efficiency catalytic aftertreatment technology for freshly manufactured engines built in 2015 and later.


Nonroad Diesel Engines

Nonroad diesel engines are used in machines that perform a wide range of important jobs. These include excavators and other construction equipment, farm tractors and other agricultural equipment, heavy forklifts, airport ground service equipment, and utility equipment such as generators, pumps, and compressors.


RICE NESHAP (Stationary Engines)

National Emission Standards for Hazardous Air Pollutants (NESHAP) applies to existing, new and reconstructed stationary Reciprocating Internal Combustion Engines (RICE). Covers stationary diesel-fueled/compression ignition (CI) RICE and stationary gas-fired engines/spark ignition (SI) RICE.


Clean School Bus

Clean School Bus is a national, innovative program designed to help communities reduce emissions from older diesel school buses. While all new buses must meet EPA’s tighter emission standards, many older school buses continue to emit harmful diesel exhaust. Diesel exhaust has a negative impact on human health in general, and especially on children because they have a faster breathing rate than adults and their lungs are not yet fully developed.


Diesel Boats and Ships

Marine diesel engines are used in a variety of different types of vessels ranging in size and application from small recreational runabouts to large ocean-going vessels. New marine diesel engines must meet increasingly stringent emissions requirements, yet these engines continue to emit significant amounts of oxides of nitrogen (NOx) and particulate matter (PM), both of which contribute to serious public health problems.


Gasoline Boats and Personal Watercraft

EPA standards for exhaust and evaporative emissions reduce the environmental impact from marine spark-ignition engines and vessels. The emission standards require manufacturers to control exhaust emissions from the engines and evaporative emissions from fuel tanks and fuel lines. This page provides general information for consumers, boaters, and other users of marine vessels that use gasoline engines (or other spark-ignition engines).



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