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Technical

Highlights

 Printed on Recycled Paper

United States

Environmental Protection

Agency

Air and Radiation EPA420-F-02-034

September 2002

Office of Transportation and Air Quality

Emission Regulations for

Stationary and Mobile Engines

The U.S. Environmental Protection Agency (EPA) has adopted

emission standards for various types of nonroad engines. As directed

by Congress in the Clean Air Act, these emission standards do not

apply to stationary engines. This fact sheet is addressed to owners of

stationary engines to answer several questions about how we

implement these requirements.

Why does it matter whether an engine is “stationary”

or “mobile”?

Congress has directed EPA to set emission standards for new nonroad

engines and prevented state and local governments from adopting any

standards for these engines, with certain exceptions. At the same time,

Congress reserved the right of state and local governments to regulate

emissions from stationary engines. As a result, we went through a

public rulemaking to establish clearly which engines are nonroad (mobile) engines and which are stationary engines.

What are examples of nonroad and stationary

engines?

Stationary engines are used in many applications where they can be

installed in a fixed location, such as power generators or irrigation
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pumps. Nonroad (mobile) applications include these same types of

equipment if they are made to be portable (or transportable). For example, a generator mounted on a pallet or a trailer would generally not be

considered stationary. Nonroad engine applications also include many

kinds of vehicles that are clearly not stationary, such as tractors, loaders,

forklifts, locomotives, and many kinds of marine vessels.

So, what exactly is a stationary engine?

Stationary engines include all internal-combustion engines that are used

either in a fixed application, or in a portable (or transportable) application in which the engine will stay at a single site for at least a full year.

Engine and equipment manufacturers need to determine before the

engine is placed in service whether their customers will use the engine in

a mobile or stationary application. This way, engine manufacturers will

appropriately build an engine (and certify it if necessary) before it

reaches its final installation. Similarly, nonroad equipment manufacturers must install only certified nonroad engines in nonroad equipment.

For example, a trailer-mounted generator would be considered stationary

only if the equipment and engine manufacturers had clear information

showing that, throughout the engine’s life, the owner would operate the

engine at single locations for at least 12 months.

What about engines that operate only at summer

construction projects?

We are aware that some work sites, such as summer construction

projects, operate for less than a full year. For engines at these seasonal

work sites, we apply a different test to determine if they qualify as

stationary engines. For a work site to qualify for having any stationary

engines, it must be in operation for at least two consecutive years with a

“work season” of at least three months. We would consider individual

engines at such a work site to be stationary if they operate as stationary

engines for a full season.

What emission standards apply to nonroad (mobile)

engines?

We have adopted emission standards for almost all nonroad engines.

These emission standards are generally tailored to the specific application and type of engine. For example, we have separate emission standards for marine engines, locomotives, and other land-based diesel
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engines (see Table 1). We also usually have separate standards for

diesel- and gasoline-fueled engines. These standards typically apply to

engine manufacturers, who certify with us that their new engines will

meet emission standards over an established period of operation with

proper maintenance and use. EPA’s nonroad emission standards generally do not affect any engines that have already been placed into service,

unless they are installed in new equipment or used in a different application (such as converting a locomotive engine to power a generator or a

vessel)1

.

In addition, California may adopt (and has adopted) standards for most

nonroad engines, which other states may copy. State and local authorities may also regulate the use and operation of nonroad engines.

What emission standards apply to stationary

engines?

EPA may adopt New Source Performance Standards (NSPS) or National

Emission Standards for Hazardous Air Pollutants (NESHAP) for stationary engines. We have not yet done so, but are expecting to propose

NESHAPs for stationary engines in 2002.

In addition, state and local agencies may adopt requirements for stationary engines. These requirements are usually designed to help areas meet

ambient air quality standards under federally mandated State Implementation Plans (SIPS), though states may also adopt requirements for other

air quality purposes. In any case, these requirements typically take the

form of a permit process in which you show that your engines use a

certain type of technology or operate at a certain emission level. Manufacturers typically take the responsibility of showing that their engines

meet these requirements, but you may have a significant responsibility

to ensure proper operation and maintenance.

Especially in rural counties, it may be that no state or local emission

standards apply. In other areas, local authorities may simply require that

engines meet EPA emission standards that apply to comparable nonroad

engines. In areas with the most need to address air quality problems,

local requirements may call for emission controls that are more chal1

 EPA’s locomotive regulations apply to certain older locomotive engines

when those engines are rebuilt.
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lenging than EPA standards. See www.cleanairworld.org/ for links to

many state and local offices that would implement requirements for

stationary engines.

What happens if someone moves a stationary

engine?

If you have a stationary engine that is not certified to EPA emission

standards, you must use it consistently with our definition of stationary

engines. Converting it to a mobile engine would require engine certification to applicable standards for nonroad engines. Anyone who moves

a stationary engine or installs it in a mobile application may be considered a manufacturer of new nonroad equipment and risks substantial

fines if the engine is not certified.

If you need to replace a stationary engine that fails prematurely, this

restriction on moving the failed engine does not apply. You may replace

it without recalculating the residence time described above.

May I use an EPA-certified nonroad engine in

stationary applications where there are no local

requirements?

 Yes. Many engine manufacturers choose to do this to avoid the complexity of offering multiple engine models and to reduce the risk of

someone using an uncertified engine in a mobile application.

Can I convert a used mobile engine to provide power

as a stationary engine?

This depends on local requirements. State or local authorities may

choose to apply emission-control requirements to these engines.

How does Customs treat imported stationary

engines?

The U.S. Customs Service works with us to enforce our requirements. If

anyone tries to import an uncertified engine without clear evidence that

it will be used in a stationary application, Customs may impound the

engine temporarily or refuse entry, depending on the circumstances. We

therefore recommend that all imported stationary engines have a perma-
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nent label identifying them as stationary engines that are not subject to

EPA’s emission standards for nonroad engines. See EPA’s declaration

form for more information about importing stationary engines at:

www.epa.gov/otaq/imports/forms/3520-21.pdf .

Table 1

Current Emission-Control Programs

Engine Category

Location in the

Code of Federal Regulations

Land-based nonroad diesel

engines

40 CFR part 89

Lawn and garden engines

(and other spark-ignition

engines under 19 kW)

40 CFR part 90

M 1 arine spark-ignition engines 40 CFR part 9

M 4 arine diesel engines 40 CFR part 9

L 2 ocomotives 40 CFR part 9

Industrial spark-ignition

engines (and other landbased engines over 19 kW)

40 CFR part 1048

R 1 ecreational vehicles 40 CFR part 105
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Where Can I Get More Information?

Additional documents on nonroad engine emission standards are available electronically on the Web site for the Office of Transportation and

Air Quality at:

www.epa.gov/otaq/nonroad.htm

Additional information related to EPA regulation of stationary engines is

available electronically on the Web site for the Office of Air Quality

Planning and Standards at:

www.epa.gov/ttn/atw/rice/ricepg.html

Document information is also available by contacting:

Nonroad Engines

ASD Information Line

Phone: (734) 214-4636

E-mail: asdinfo@epa.gov

Stationary Engines

Sims Roy

919-541-5263

E-mail: roy.sims@epa.gov