Small Non-Road Engines

Phase 3 regulations for small engines finalized Sept. 4, 2008 (EPA Tightens Engine Standards on Surf and Turf). This Border Center web page will be updated in the near future.

Click here to watch Judy Pino discuss new EPA standards for small engine emissions with Lori Stewart, Associate Office Director of EPA's Office of Transportation ...

EPA Video


Since the mid-1990s, air emissions from small engines have been regulated by U.S. Environmental Protection Agency (EPA) rules, promulgated under the Clean Air Act (CAA). New, more stringent proposed standards that have not been finalized were published in 2007.

These rules cover items such as lawnmowers, chain saws, string trimmers (“weed whackers”), and other lawn and garden power equipment, as well as small generators and construction and farm power tools. Many such items that are sold by retailers in the U.S. are manufactured abroad, and many imported small engines have proven to be in violation of the existing EPA standards.

When the rules first came into effect, EPA and U.S. Customs and Border Protection (CBP) focused their enforcement efforts on foreign manufacturers, importers, and brokers. More recently, EPA and other federal agencies have extended their enforcement efforts to the retail level.

Retailers, and all others involved in importing or selling small engines, should be aware that existing regulations require each engine sold in the U.S. to be certified and labeled. In addition to being a compliance requirement, these regulations, together with advances in fuel formulation and combustion technology, are significantly reducing air emissions. For example, certified engines now emit two to three times lower emissions than uncertified engines.

This web page provides an overview of the small engine regulations and the associated import rules, as well as a summary of current issues relating to this topic.

Emissions Impacts

Roughly half of the air pollution in the U.S. is caused by on-road and nonroad engines. These mobile sources of air pollution include cars, trucks and buses, as well as the wide range of gasoline and diesel engines found in nonroad equipment used in construction, agriculture, and lawn and garden equipment, in dirt bikes, and as marine engines. The air pollutants emitted by mobile sources include:

  • particulate matter
  • volatile organic compounds (VOC)
  • air toxics
  • oxides of nitrogen (NOx)

These air pollutants have been linked to many respiratory health problems, such as asthma, heart disease and cancer.

Although small gasoline engines are used much less than automobiles, their impact is disproportionably large:

  • one hour of weed whacking typically generates as many hydrocarbon and air toxic emissions as 850 miles of in-town driving
  • a push mower emits as much pollution in one hour as 11 cars
  • a riding mower emits as much in one hour as 34 cars

Overall, small engines such as those used in lawn and garden equipment, are estimated to contribute over 5% to the volatile organic compound (VOC) and carbon monoxide (CO) emission inventories in populated areas where air pollution levels persistently exceed National Ambient Air Quality Standards (i.e., non-attainment areas).

Air Emissions Regulations

Most people think that air pollution control programs in the U.S. apply primarily to cars, trucks, and large industrial facilities. But in 1990, responding to a request from Congress, EPA began to look at other sources of air pollution including:

  • recreational vehicles
  • farm equipment
  • construction equipment
  • boats
  • locomotives
  • lawn and garden power equipment

(These types of sources are commonly referred to as “nonroad mobile sources”.) Since then, EPA has been developing emission standards for virtually all types of nonroad equipment, including the types of small spark-ignition engines of 25 HP (19kW) or less that are predominately used in lawn and garden power equipment and in some farm construction and utility equipment.

Small engines are classified by EPA by size, and according to whether they are handheld or non-handheld. The table below shows EPA’s classification scheme for spark-ignition engines. Typical applications for the nonhandheld categories include:

  • Class I engines, used primarily in walk-behind lawnmowers
  • Class II engines, used primarily in lawn and garden tractors

The handheld categories include:

  • Class III and IV engines, used primarily in residential equipment such as string trimmers, leaf blowers and chainsaws
  • Class V engines, used primarily in commercial equipment such as chainsaws
Table 1: Small SI Engine Classes


Class I-A
Class I-B
Class I
Class II
Class III
Class IV
Class V
<66 cc
66 to <100 cc
100 to <225 cc
≥225 cc
<20 cc
20 cc to <50 cc
≥50 cc

The existing and proposed EPA rules for small engines include:

  • Phase 1 (Promulgated 1995). Phase 1 introduced an initial level of emission standards for both handheld and non-handheld equipment and a certification process. The rule set allowable exhaust levels for hydrocarbons (HC), carbon monoxide (CO), and NOx and it applied to all small engines produced after September 1, 1997 (with some earlier and a few later, depending on type). Allowable Phase 1 emission levels vary, depending on engine size and use. [Phase 1 Fact Sheet.]
  • Phase 2 (March 1999, April 2000). Phase 2 included tighter emission standards for engines used in handheld equipment applications for HC+NOx (in grams per kilowatt-hour (g/kW-hr)). The standards were to be phased in over a number of years, to give the manufacturers time for an orderly and efficient transition of engine designs. In addition, the Phase 2 rule included new programmatic requirements to ensure that engines meet the tighter standards throughout the useful life of the equipment. [More information on Phase 2.]
  • Phase 3 (Proposed May 2007). In 2007 EPA proposed HC+NOx exhaust emission standards of 10 g/kW-hr for Class I engines starting in the 2012 model year, and 8 g/kW-hr for Class II engines starting in the 2011 model year. EPA expects manufacturers to meet these standards by improving engine combustion, and by adding catalytic converters. These standards are consistent with the requirements recently adopted by the California Air Resources Board (see State Initiatives below). With Phase 3, EPA did not propose new exhaust emission standards for handheld emissions. However, they did propose new evaporative emission standards for both handheld and nonhandheld equipment. The new standards include requirements to control fuel tank permeation, fuel line permeation, and diffusion emissions. For nonhandheld engines, EPA proposed to require control of running losses. When fully implemented, the proposed Phase 3 standards are expected to result in a 35 percent reduction in HC+NOx emissions from new engines’ exhaust and a 45 percent reduction in evaporative emissions. [Phase 3 Federal Register Notice.]

Before a small engine can be sold in the U.S., it must be certified and labeled for conformity with the applicable regulations. In order to obtain a certificate of conformity, test data must be submitted to EPA, together with other information demonstrating that the engine meets applicable standards. Before importation or sale, each certified engine must be labeled to indicate compliance with the rules. If an engine is not properly labeled, the engine is presumed by EPA and CBP to be uncertified. Therefore, the importer would not be permitted to import the engine or sell it in the U.S.

Ordinarily, the engine manufacturer, not the importer, obtains EPA certification for imported engines. However, an engine importer also may apply to EPA for a certificate, on the condition that the importer assumes all the responsibilities of the manufacturer.

Air Emissions Regulations -- State Initiatives

With the exception of California, states have implemented mobile source air pollution rules that are consistent with the federal standards. California, however, has taken initiatives to further control emissions from most mobile sources, including small engines (25 HP or less). The California Air Resources Board - Mobile Source Program has established two tiers of requirements for small engines:

  • Tier I was implemented in 1995 and regulates emissions of hydrocarbons, NOx, particulate matter, and CO to varying degrees based on the displacement of the engine. Tier II became effective for model year 2000 and will continue to regulate hydrocarbons, NOx, particulate matter, and CO emissions through 2010.
  • Tier II established durability requirements for emissions-control systems. Therefore, engine manufacturers must demonstrate that the equipment's emissions levels remain low for periods ranging from 50 hours to 500 hours, depending on the displacement of the engines and whether the equipment is residential or commercial.

California also has evaporative emissions performance and design standards for gasoline-fueled, spark-ignited small off-road engines rated at equal to or less than 19 kilowatts, and equipment utilizing such engines. The standards apply to applicable engines model years 2006 through 2013. Engine manufacturers may opt to comply with either the emissions or design standards.

Importer and Manufacturer Responsibility

Both the original engine manufacturer (the company that assembles the engine) and the importer are responsible for ensuring that engines imported to the U.S. comply with all certification standards and requirements. For example, importers and manufacturers are prohibited from importing or manufacturing engines that are not properly EPA-certified and labeled. EPA highly recommends that importers inspect the engines they intend to import to verify that they are EPA-certified and labeled. Importers are also responsible for ensuring that the engine manufacturer will honor the emissions warranty. (This warranty is separate and apart from any other manufacturer warranty.) Depending on engine type and size, the warranty period may vary from two to five years. The importer also bears responsibility for any requirements not met by the original engine manufacturer. For more information, see:

Importers of gasoline and diesel-powered nonroad equipment must complete EPA Declaration Form 3520-21, which requires confirmation of EPA certification or a description of the applicable exemption. Form 3520-21 must be submitted to U.S. Customs and Border Protection (CBP) upon request along with other CBP entry documents.

Uncertified engines that are ultimately destined for a foreign country must bear export-only labels on the engine and the container. An EPA Declaration Form 3520-21 must be completed and an appropriate bond must be paid.


When EPA or CBP determines that imported equipment does not meet the EPA emissions certification requirements, CBP detains or seizes the equipment. EPA and CBP then coordinate on taking enforcement actions to address the CAA violations, including collection of a penalty and exportation of the illegal equipment. The maximum penalty is $32,500 for each illegal engine, although penalties may be reduced for first-time violators and for importers who voluntarily disclose and remedy the violation and all prior violations. CBP or EPA may also initiate a criminal action against an importer who knowingly makes false or fraudulent statements, or who omits material information required in CBP entry documents. Persons who commit these crimes are subject to a fine of up to $250,000 or imprisonment for up to two years, or both. [For more information on enforcement cases, see MTD and Jenn Feng Clean Air Act Settlement and US EPA Clean Air Act Mobile Source Importation Settlement Information.]

Policies That Reward Compliance

EPA has two policies that reward companies that bring themselves into compliance with environmental laws:

These policies encourage greater compliance by substantially reducing or eliminating penalties for entities that voluntarily discover, disclose and expeditiously correct violations of environmental law.

Import IssuesGenerator

Imports of small engines used in non-road equipment such as small tractors, lawnmowers, off-road motorcycles, all-terrain vehicles and generators are surging. Many of these engines are from Asia, with a dramatic increase in imports from China over the past several years. A portion of these engines are not certified to meet emission standards under the Clean Air Act. The situation is made worse by the dramatic increase in the number of foreign manufacturers of the equipment and the increase in inexperienced U.S. companies and individuals who import it. Illegal equipment is being offered for sale to customers in this country through retail outlets and, increasingly, over the Internet.

In July of 2007, President Bush signed Executive Order 13439 establishing an Interagency Working Group on Import Safety. This Working Group consists of over ten government agencies including EPA and the Departments of Health and Human Services, Homeland Security, State, Treasury, Justice, Agriculture, and Transportation. The wide range of agencies involved in this Working Group illustrates the breadth of import issues. One of the recommendations of the Interagency Working Group on Import Safety was to consider a strategic focus or initiative, using existing statutory and regulatory authorities, and, based upon Agency priorities, increase enforcement actions against foreign and domestic manufacturers, as well as importers, brokers, distributors, and retailers who introduce illegal goods into the stream of commerce. This rulemaking will EPA's Rulemaking "Control of Emissions from Nonroad Spark-Ignition Engines and Equipment" seeks to clarify for all regulated parties, including retailers, that liability for the importation of products in violation of the Clean Air Act and/or its implementing regulations extends beyond the manufacturer and direct importer of the product.

More Information

Lawn and Garden (Small Gasoline) Equipment. In April 2007, EPA proposed a new emission control program that would reduce hydrocarbon emissions from small spark-ignition engines by about 35 percent. The new exhaust emissions standards would begin in 2011 or 2012, depending on the size of the engine. The proposal also includes new standards to reduce evaporative emissions from these fuel systems.

Nonroad engines, equipment and vehicles. Nonroad engines are used in an extremely wide range of applications, each involving great differences in operating characteristics, engine technology, and market dynamics. EPA has adopted emission standards for nearly all types of nonroad engines, equipment, and vehicles.

Engine Certification Data. This page provides certification data from various engine manufacturers for past and current model years.

Nonroad Confirmatory Testing for Small Spark-Ignition (SI) and Compression-Ignition (CI) Engines. This document includes the steps for nonroad confirmatory testing for small spark-ignition (SI) and nonroad compression-ignition (CI) engines at EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL).

Motor Vehicle and Engine Compliance Program (MVECP ) Fees Information. Information pertaining to the current and proposed rules that administer fees for the services provided under the MVECP.

40 CFR Part 90: Control of Emissions from Nonroad Spark-Ignition Engines at Or Below 19 Kilowatts. Codified rules pertaining to emissions from nonroad spark-ignition engines at or below 19 kilowatts.

Enforcement Alert: EPA Enforcing Stringent Standards for All Nonroad Engines (Sept. 2006). A useful compliance assistance resource that contains information on applicable enforcement actions regarding small engines.

Enforcement Alert Many Scooters and Off-Road Motorcycle Imports Fail to Meet EPA Standards (August 2005). A useful compliance assistance resource that contains information on imported scooters and off-road motorcycles, including manufacturer and importer requirements.

Visit our other Border Center sites: Canadian Border | Port Compliance | Mexican Border | China Exports