U.S. ENVIRONMENTAL PROTECTION AGENCY   	EPA 420-F-94-003
         OFFICE OF MOBILE SOURCES

  Nonroad Engines and Air Pollution
What is a Nonroad Engine
"Nonroad" is a relatively new term that covers a diverse collection of engines,
equipment, and vehicles. Also referred to as "off-road" or "off-highway," the
nonroad category includes outdoor power equipment, recreational vehicles, farm
and construction equipment, boats, and locomotives.


Nonroad Engines and Air Pollution
Most nonroad equipment and vehicles are powered by engines that burn gasoline
or diesel fuel. Pollution from these  engines comes from by-products of the
combustion process (exhaust) and,  for gasoline-fueled engines, from evaporation
of the fuel itself.

Electric equipment is cleaner than equipment powered by gasoline engines.
Electrically-powered lawn and garden tools produce essentially no pollution
from exhaust emissions or from fuel evaporation. However, even electric equip-
ment is not pollution-free, because  power plants that generate the electricity do
pollute.

Emission control for nonroad engines has not been a major design consideration
until now because of their relatively lower overall contribution to air pollution.
Consequently, these engines are much less clean than highway vehicles, which
have been subject to regulatory controls for more than 20 years. Emissions from
nonroad engines contribute  as much as 15 to 20 percent of unhealthy pollution in
cities across the United States.
Pollutants From Nonroad Engines
Pollutants from nonroad sources include:
Hydrocarbons - unburned or partially burned fuel molecules that react in the
atmosphere to form ground-level ozone, a major component of smog. Some hydro-
carbons are toxic and may cause cancer or other health problems. Another
source of hydrocarbon pollution from nonroad engines is fuel evaporation, which
occurs when gasoline vapors are forced out of the fuel tank (as, for instance,
during refueling) or when gasoline is spilled and evaporates.
Particulate matter - an exhaust product primarily from diesel-fueled vehicles,
these microscopic airborne particles damage the respiratory system and
                                                     FACT SHEET OMS-20 .
                                                         May, 1996

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         Nonroad Engines
 contribute to the smoke and odor associated with diesel exhaust.
 Nitrogen oxides - the result of subjecting nitrogen and oxygen in the air to the
 high temperature  and high pressure conditions in an internal-combustion en-
 gine. Nitrogen oxides react with hydrocarbons in the atmosphere to form ground-
 level ozone. Nitrogen oxides also contribute to acid rain.
 Carbon monoxide - a colorless, odorless, poisonous gas that results from
 incomplete fuel combustion.
 Carbon dioxide - the ultimate product of burning carbon-based fuel. Carbon
 dioxide does not directly impair human health, but it is a "greenhouse gas" that
 contributes to the  potential for global warming. As engine fuel economy declines,
 carbon dioxide emissions increase.

 Controlling Nonroad Emissions
 The 1990 Clean Air Act specifically directs the U.S. Environmental Protection
 Agency (EPA) to study, and regulate if warranted, the contribution of nonroad
 engines to urban air pollution.  A 1991 EPA study documented higher than
 expected emission levels across a broad spectrum of engines and equipment.
 Emission reductions are being sought from the following engine types:

 •     Small spark-ignition (mostly gasoline-fueled lawn and garden equipment)
 •     Large compression-ignition (mostly diesel-fueled farm and construction
       equipment and commercial marine vessels)
 •     Marine propulsion engines (mostly gasoline-fueled pleasure craft)
 •     Recreational spark-ignition (mostly used in snowmobiles, all-terrain
       vehicles, dirt bikes, and go-carts)
 •     Locomotives

 EPA and industry are working together on a comprehensive strategy to reduce
 these emissions. One part of that strategy is a public information program to
 show consumers how to prevent pollution from nonroad engines by reducing
 gasoline spillage and choosing clean equipment. Another part of the strategy will
 establish a regulatory process that sets emission standards for several categories
 of nonroad engines.


 For More Information:
 The Office of Mobile Sources is the national center for research and policy on air
 pollution from highway and off-highway motor vehicles and equipment. You
 can write to us at the EPA National Vehicle and Fuel Emissions Laboratory,
 2565 Plymouth Road, Ann Arbor, MI 48105. Our phone number is (313) 668-4333.
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