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Owners or operators of portable engines and other types of equipment can register their units under the CARB Statewide Portable Equipment Registration Program (PERP) in order to operate their equipment throughout California without having to obtain individual permits from local air districts.

The PERP program is available to portable engines 50 horsepower or greater of any fuel type. Example of equipment that is eligible includes crushers, screening plants, wood grinders, concrete batch plants, abrasive blasting, etc.

CARB has recently amended the PERP regulation and Portable Engine ATCM. For more information please review the following booklet:

PERP Frequently Asked Questions

For all requirements and more on the application process, visit the PERP PROGRAM PAGE.


The Airborne Toxic Control Measure (ATCM) regulates particulate matter (PM) from portable diesel engines rated 50 horsepower and greater. For applicability and exemptions, review the regulation text. The ATCM reduces PM by the removal of tier 0 engines, restricting older engines from entering California and imposing fleet emission reduction requirements.

This regulation splits portable engine fleets into two sizes:

  • Small fleets: All engines in fleet add up to 750 or less total brake horsepower (bhp)
  • Large fleets: All engines in fleet add up to more than 750 total bhp

The following table outlines the required tier phase out schedule for small and large fleets.

Tier Phase-out Schedule
(required for small fleets, default option for large fleets)
Engine Certification Engines Rated 50 - 750 bhp Engines rated over 750 bhp
Large Fleet Small Fleet
Tier 1 1/1/2020 1/1/2020 1/1/2022
Tier 2 built prior to 1/1/2009 1/1/2022 1/1/2023 1/1/2025
Tier 2 built on or after 1/1/2009 NA NA 1/1/2027
Tier 3 built prior to 1/1/2009 1/1/2025 1/1/2027 NA
Tier 3 built on or after 1/1/2009 1/1/2027 1/1/2029 NA
Tier 1, 2, and 3 flexibility engines December 31 of the years after the date of manufacture. This provision shall not apply to any engine operation before the effective date of this regulation.

Large fleets may opt to use the previously enforced fleet average option instead on the tier phase out table option shown above. Fleets opting for this compliance pathway must send a written request to CARB by 6/30/19 and all engines must be registered in PERP.
Fleet Average Standards
(option for large fleets only)
Compliance Date Fleet PM Stanard (g/bhp-hr)
1/1/2020 0.10
1/1/2023 0.06
1/1/2027 0.03

To learn more about requirements of the ATCM regulation visit the PERP PROGRAM PAGE.
To get specifics on what is required in your county, contact your LOCAL AIR DISTRICT CONTACT.


June 30, 2019 – Deadline for large portable engine fleets to request the Fleet Average Standards compliance pathway.

January 1, 2020 – Tier 1 portable engines, rated equal to or less than 750 bhp, must be phased out.

January 1, 2022 – For large fleets only: Tier 2 portable engines, rated equal to or less than 750 bhp and built on or after 1/1/09, must be phased out.

January 1, 2022 – Tier 1 portable engines rated greater than 750 bhp, must be phased out.