Frequently Asked Questions from
Owners and Operators of Nonroad
Engines, Vehicles, and Equipment
Certified to EPA Standards
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What requirements apply to owners and operators of certified products?
A key part of the regulations that applies to you is the tampering prohibition—you may not
disable any emission controls installed on certified engines, vehicles, or equipment. This would
apply for removing emission control devices, adding or modifying hardware or software that
increases emissions (of any pollutant), reprogramming onboard computers, or operating engines
without any needed supplies such as Diesel Exhaust Fluid. Manufacturers explain in their own-
er's manual what type of emission controls exist for each model; they may also specify some
minor maintenance that must be done to keep emission controls working properly. For restrictions
and recordkeeping requirements that apply for rebuilding engines and performing maintenance
on certified products, see "How to Maintain or Rebuild Engines Certified to EPA Standards,"
(EPA-420-F-18-003, February 2018) which is available at www.epa.gov/regulations-emissions-
vehicles-and-engines/regulations-emissions-nonroad-vehicles-and-engines.
Similarly, EPA regulations prohibit defeat devices—you may not make, sell, or install any part
that bypasses, impairs, defeats, or disables the control of emissions of any regulated pollutant.
Since manufacturers have the primary responsibility to meet emission standards for their products,
you generally have no requirements to achieve a certain level of emission control or to re-certify.
However, you must meet additional requirements in two special circumstances:
•	You may need to use certified kits or systems when remanufacturing locomotive engines
or marine diesel engines.
•	In the case of Marine SI engines (40 CFR part 1045), Recreational vehicles (40 CFR
part 1051), and Small SI engines (40 CFR part 1054), you must re-certify if you up-
grade your engine to operate on a different fuel. For fuel conversions with other types of
nonroad engines, vehicles, or equipment, you may need to do testing to show that the
conversion is not considered tampering, but you do not need to re-certify.
What kind of emission controls does EPA require?
We don't tell manufacturers what emission controls to use to comply with the regulations, but
we rely on testing information from engines equipped with specific technologies to establish the
emission standards. Manufacturers may use these anticipated technologies, or they may find
better ways to meet emission standards.
Manufacturers of diesel engines have typically met the standards with more careful control of
intake air and fuel injection, with some exhaust gas recirculation. Long-term standards for many
of these engines will generally involve additional use of aftertreatment devices such as diesel
particulate filters (DPF) and selective catalytic reduction (SCR).
Most Large SI engines and many Marine SI engines use automotive-type technologies, including
closed-loop fuel injection and three-way catalytic converters. For other engines, manufacturers
will optimize air-fuel mixtures and make other internal engine changes. We expect continued
use of two-stroke engines in the following cases: (1) outboard and personal watercraft marine
engines may use direct-injection two-stroke engine technology, which avoids the most prob-
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lematic aspects of two-stroke combustion; (2) to maintain lightweight performance, Handheld
Small SI engines will typically continue to use two-stroke engines, though these engines will
generally have catalysts to reduce the amount of unburned fuel from escaping through the
exhaust as hydrocarbon emissions; and (3) some two-stroke snowmobile engines will likely con-
tinue to be available, depending on ongoing efforts to improve the performance characteristics
of four-stroke snowmobile engines.
For gasoline-fueled products, we have also adopted requirements to control permeation emis-
sions from fuel systems. We expect these requirements to lead to the use of improved materials
to prevent fuel from escaping through fuel tanks and hoses into the atmosphere. This should
noticeably reduce the smell of gasoline around these vehicles and equipment.
How will these controls affect performance and safety?
As part of the rulemaking process, we evaluate potential safety issues related to new standards
to make sure not to adopt emission standards that would cause manufacturers to use emission
controls that add new risks to operating vehicles or equipment. As always, it is important to
take proper precautions when using engine-powered vehicles or equipment.
Meeting emission standards adds to the engine designer's challenge. This might lead to some
trade-offs with respect to power or efficiency; however, there are many examples of design
engineers coming up with ways to add emission controls in a way that significantly improves
engine power and efficiency while reducing emissions. Over time, engineers will work to
improve designs to reduce or eliminate any remaining trade-offs.
Do EPA regulations affect where I can use my nonroad vehicle or equipment?
No. These regulations do not include any specific restrictions about where you can use your
nonroad vehicle or equipment. They address only the permissible emission rates from new,
certified products.
State and local governments have limited authority to set emission standards for new products;
however, they may adopt regulations that restrict the use and operation of most products that
are no longer new. EPA generally has no involvement with such restrictions.
Do EPA regulations apply in California?
California has adopted its own emission standards for certain types of new nonroad engines,
vehicles, or equipment. In those cases, manufacturers must certify their products with the
California Air Resources Board; these products are also certified with EPA even if no additional
requirements apply.
EPA's prohibitions against tampering and defeat devices apply to certified products throughout
the United States, including products that are certified to meet emission standards that apply
uniquely in California.
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For More Information
You can access documents related to emission standards for nonroad engines, vehicles, and
equipment on EPA's Office of Transportation and Air Quality (OTAQ) website at:
www.epa.gov/regulations-emissions'vehicles'and'engines/regulations'emissions'
nonroad-vehicles-and-engines
You can also contact the OTAQ library for document information at:
(734) 214-4311
Email: Group_AALibrary@epa.gov
Table 1
Schedule for Application of New Emission Standards for Certifying Engines and Vehicles
Engine category
Engine subcategory
Manufacturing date
after which emission
standards start to apply
A. Heavy-duty highway engines

Model year 1970
B. Locomotives or locomotive
engines

January 1, 1973
C. Marine compression-ignition
engines at or above 37 kW
Commercial: displacement < 0.9 L/cyl
Model year 2005
Commercial: 0.9 < displacement < 2.5 L/cyl
Model year 2004
Commercial: displacement > 2.5 L/cyl
Model year 2007
Recreational: displacement < 0.9 L/cyl
Model year 2007
Recreational: 0.9 < displacement < 2.5 L/cyl
Model year 2006
Recreational: 2.5 < displacement < 5.0 L/cyl
Model year 2009
D. Other nonroad compression-
ignition engines.
Marine compression-ignition engines: Power < 19 kW
January 1, 2000
Marine compression-ignition engines: 19 kW< Power < 37
January 1, 1999
Nonroad engines: Power < 19 kW
January 1, 2000
Nonroad engines: 19 kW< Power < 37
January 1, 1999
Nonroad engines: 37 kW< Power < 75
January 1, 1998
Nonroad engines: 75 kW< Power < 130
January 1, 1997
Nonroad engines: 130 kW < Power < 560
January 1, 1996
Nonroad engines: Power > 560 kW
January 1, 2000
E. Marine spark-ignition engines.
Outboard
Model year 1998
Personal watercraft
Model year 1999
Sterndrive/inboard
Model Year 2010
F. Recreational spark-ignition
engines and vehicles
—
Model year 2006
G. Other nonroad spark-ignition
engines at or below 19 kW
—
Model year 1997
H. Other nonroad spark-ignition
engines above 19 kW
—
Model year 2004
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