Small Off-Road Engines (SORE)

This page last reviewed February 19, 2013


Background:

image of a man mowing the lawn The small off-road engine (SORE) category consists of off-road spark-ignition engines below 25 horsepower, including small utility equipment, lawn mowers and weed trimmers. This category does not include compression-ignition engines, watercraft, or recreational vehicles. The following includes general information regarding small off-road engines and ARB's SORE program:

What's New:


  • The final SORE amendments, which were adopted by the Air Resources Board on December 16, 2011, were filed with the California Office of Administrative Law (OAL) on October 26, 2012. OAL has until December 12, 2012, to render a decision. On March 22, 2012, a Notice of Public Availability of Modified Text was posted and made available for a fifteen-day public comment period. On November 15, 2011, a Notice of Change in the Public Hearing Date was posted, which rescheduled the date of the hearing from December 15, 2011, to December 16, 2011. On November 4, 2011, an Errata was posted to provide minor corrections to the staff report that had been posted October 26, 2011. The applicable regulatory documents for the above indicated actions can be found at the following link:
  • On December 15, 2011 the Air Resouces Board will consider proposed amendments to the California regulations and test procedures for SORE/LSI/OHRV/Off-Road CI/Rec Marine.  Specifically, the discussion will focus on test procedures for SORE and Tier 4 Off-Road CI, and the exhaust emission test fuel for off-road SI engines, equipment, and vehicles. The meeting notice, staff report, and all other regulatory documents can be found at the following link:
  • The Air Resouces Board (ARB) has released a draft of the proposed amendments to the small off-road engines (SORE) regulation, effective on May 5, 2010.  The draft proposal can be found on the following webpage:
The ARB is planning on proposing modifications to the California SORE regulations in order to harmonize its test procedures with the U.S. Environmental Protection Agency's (U.S. EPA) rules.  The proposal will sunset the current test procedures with the 2012 model year and adopt portions of U.S. EPA's Parts 1054 and 1065, of Title 40, Code of Federal Regulations (published on November 8, 2010).  Because California has different air quality goals than the rest of the country, some portions of Parts 1054 and 1065 have been either modified as necessary for California's purposes or excluded entirely.  For example, U.S. EPA and ARB have different emission credit programs.  Accordingly, ARB has excluded portions of U.S. EPA's provisions that refer to their credit program.  The ARB proposal is scheduled to be considered for adoption at the December 2011 Board Hearing.  

In addition to proposing adoption of these harmonizing modifications, ARB is proposing to change the SORE certification exhaust test fuel to a ten-percent ethanol blend (E10).  This change is being considered so that the certification test fuel used for California's off-road gasoline-fueled engine and equipment categories remains consistent with the planned E10 changes to the on-road motor vehicle certification test fuel requirements.  Please note that because the ARB is in only the early stages of considering this modification, the attached documents do not specifically reflect this proposed change.  Nevertheless, we are seeking comments from interested parties on this important issue.  

In order to satisfy the required deadlines that are involved in this process, comments related to the draft proposed amendments should be received by the close of business on Monday, August 8, 2011.  Please email comments to Ms. Yun Hui Park, Lead Staff, with a copy to Mr. Ronald Haste, Manager, Off-Road Control Section.

  • OAL approved the rulemaking and filed it with the Secretary of State on April 5, 2010.  The regulation will become effective on May 5, 2010.  The final regulation order can be found at the following link:

  • The Resubmittal Package for the Small Off-Road Engines regulations was filed with OAL on February 24, 2010. OAL has until April 9, 2010 to make a determination.  The final regulation order, addendum to the final statement of reasons, and other regulatory documents can be found at the following link:

  • ARB will be holding a workshop on November 17, 2009 to discuss the California regulations and test procedures for small off-road engines (SORE) with respect to Zero Emission Equipment (ZEE).  Staff would appreciate any constructive comments on the proposed changes.  The workshop notice is available for viewing or downloading from the following page:
  • On November 21, 2008, the Air Resources Board approved proposed amendments to the California regulations and test procedure for small off-road engines (SORE).  Specifically,  modifications were made to the SORE emissions credit program and other minor changes to the regulatory language.  The meeting notice, staff report, and all other regulatory documents can be found at the following link.

  • On April 21, 2008, ARB hosted a public workshop to discuss proposed amendments to the California regulations and test procedure for small off-road engines (SORE) and large spark-ignition engines with an engine displacement less than or equal to one liter (LSI ≤ 1 L).  Specifically, the discussion will focus on standards for LSI ≤ 1 L, modifications to the SORE emissions credit program, and other minor changes to the regulatory language.  This is the second workshop in continuation of the rulemaking process. The proposed regulations are scheduled to be presented to the Board at the November 20-21, 2008 hearing. (Note:  Board Hearing date change)

  • On November 14, 2007, ARB hosted a public workshop to discuss the proposed changes to California's regulations and test procedures for new SORE and equipment and LSI engines and equipment with engines < 1 liter displacement. Specifically, the discussion focused on standards for LSI engines < 1 liter displacement, modifications to the SORE emissions credit program, and other minor changes in the SORE regulatory language. The workshop notice and presentation can be found below.

Past Regulatory Activity:


The ARB staff is developing SORE regulations to further reduce emissions from this category. Initially, the staff had sought to develop separate exhaust and evaporative emission control measures for this category. After further review, and at the request of industry, a decision was made to jointly develop a control measure to reduce evaporative, permeation, and exhaust emissions. This control measure was presented to the Board at the September 25, 2003 Board hearing.

A calendar of events has been prepared to provide information regarding the timing of testing and public workshops leading up to the Board hearing (PDF - 68K).  View the Public Hearing Notice and related materials, including the Staff Report and Proposed Regulations and Test Procedures, for the Small Off-Road Engine and Equipment proposed rulemaking.


The Board approved the SORE regulations in 1990 and requested ARB staff to return with a status report twice before the 1999 implementation of the second tier standards. The first tier standards took effect in 1995 and required manufacturers to produce clean engine versions of their handheld and non-handheld equipment. The first status report went to the Board in January 1996. ARB staff met with engine manufacturers and other stakeholders to re-evaluate the 1999 standards. ARB staff proposed changes in the 1999 standards at a board hearing held on March 26, 1998 (please see the mailout #MSC 98-02). These amendments to the regulations were approved by OAL in March 1999.


  • Please view our formal regulatory documents regarding the Small Off-Road Engine Regulations. These documents include, but are not limited to, the staff report, regulations, test procedures, and 15-day notice(s).

What's New Archive:


  • The Third Notice of Public Availability of Modified Text regarding modifications to the Small Off-Road Engine regulations was posted on June 30, 2004. 
  • The Second Notice of Public Availability of Modified Text regarding modifications to the Small Off-Road Engine regulations was posted on May 14, 2004.
  • "Staff Report - Report to the Board on the Potential Electrification Programs for Small Off-Road Programs." (PDF - 352K)
  • At the September 25, 2003, Board Hearing, the staff presented and the Board approved modifications to the Small Off-Road Engine regulations originally proposed in the Staff Report (released on August 8, 2003) in response to comments received since the Staff Report was published. View the  Notice of Public Availability of Modified Text describing the modifications has been posted to the Small Off-Road Engine Regulatory Activity web page.
  • Durability of Low Emissions Small Off-Road Engines - Final Report (PDF - 2,048KB)
    • Appendices (PDF - 199MB)  (PLEASE NOTE!!!  This is a very large file.) 
  • Off-Road Modeling Change Technical Memo (PDF - 317K)  And see additional SORE inventory related information.
  • Revised Draft Evaporative Regulations, Test Procedures, and Certification Procedures 
  • Draft Exhaust Emissions Regulations and Test Procedures
    • Draft Regulatory Amendments (MSW - 103K)
    • Draft New Test Procedures for 2005 and Later Model Year Engines (MSW - 156K)
  • Draft SORE Evaporative Emissions Methodology (PDF - 514K)
  • Revised Draft Evaporative Emission Certification Procedures (MSW - 2248K) 
  • Diurnal Testing of Off-Road Equipment Retrofitted with Carbon Canister Evaporative Emission Control Systems (March 2003) (PDF - 148K) 
  • Durability Testing of Barrier Treated High-Density Polyethylene Small Off-Road Engine Fuel Tanks (March 2003) (PDF - 98K) 
  • Results of Diurnal Emissions Testing of Walk-Behind Mowers Configured With Fuel Tank Pressure Relief Valves (PDF - 188K) 
  • Results of Durability Testing of Barrier Treated High Density Polyethylene Small Off-Road Engine Fuel Tanks (PDF - 93K)
  • Letter Requesting Individual Manufacturer Meetings with Staff Regarding Information on the Development of Emission Control Technologies for Small Off-Road Spark-Ignition Engines (PDF - 72K)
  • Letter Requesting Comments on the Draft Exhaust Emission Test Plan PDF - 250K)
  • SORE Exhaust and Evaporative Control Measure Integration Announcement (PDF - 67K)

Presentations

  • ARB staff presented information on new exhaust and evaporative regulatory requirements at the October 2005 Outdoor Power Equipment Institute Exposition. Staff's presentations are linked below.
  • ARB staff participated in a seminar at the September 2004 Outdoor Power Equipment Institute Exposition to discuss California's new 2005 and later small off-road engine regulations. The followign is a link to staff's presentation discussing the new evaporative emission certification requirements. PDF - 206 KB)
  • Staff's Presentation from the September 25, 2003, Board Hearing (PDF - 788K)
Frequently Asked Questions:
  • Leaf Blower Report - The ARB prepared a report to the State Legislature on the health and environmental impacts of leaf blowers on leaf blower operators and the general public.
  • "Staff Report - Report to the Board on the Potential Electrification Programs for Small Off-Road Programs" (PDF - 352K)

Where Can I Get More Information:

  • For more information regarding exhaust emissions, please contact Yun Hui Park at (626) 450-6263.
  • For more information regarding evaporative emissions equipment certification, please contact Kumar Muthukumar at (626) 575-7040.
  • For more information regarding evaporative emissions component certification, please contact Don Ridgley at (916) 322-8913.
  • For more information regarding the SORE evaporative emissions inventory and methodology, please contact Walter Wong at (626) 450-6184 or David Chou at (626) 450-6136.


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