CARB Regulations for TRUs

The California Air Resources Board (CARB) has approved amendments to its current rule for Transport Refrigeration Units (TRUs) operating in the state. The 2022 amendments—which increase the use of zero-emission (ZE) technology, are designed to protect the health of the public and the environment.

Latest CARB proposed regulations

Beginning December 31, 2022


  • Model-year 2023 and newer trailer TRUs, domestic shipping container TRUs, railcar TRUs, and TRU generator set engines must meet a lower particulate matter (PM) emission standard that aligns with the United States Environmental Protection Agency Tier 4 final off-road PM emission standard for 25-50 horsepower engines.


  • Newly-manufactured truck TRUs, trailer TRUs, and domestic shipping container TRUs must use a refrigerant with a global warming potential (GWP) less than or equal to 2,200, or no refrigerant at all.

Beginning December 31, 2023


  • Owners of refrigerated warehouses and distribution centers, grocery stores, seaport facilities, and intermodal railyards with a building size of 20,000 square feet or larger, must register with CARB, pay fees every three years, and report all TRUs that operate at their facility. Alternatively, they may attest that only compliant TRUs operate at their facility.

Fees and reporting

  • TRU owners are required to report all TRUs (including those based out-of-state) that operate in California to CARB, pay TRU operating fees, and affix CARB compliance labels to their TRU every three years.

Lessors and lessees

  • TRU owners (lessors) may delegate compliance responsibility to the TRU operator (lessee) if the rental or lease agreement is one year or longer.


  • Requirement: TRU owners are required to turnover at least 15% of their truck TRU fleet (defined as truck TRUs operating in California) to ZE technology each year (for seven years). All truck TRUs operating in California are required to be zero-emission by December 31, 2029.
  • Assurances: Manufacturers of ZE truck TRUs shall be required to provide a comprehensive warranty for ZE truck TRUs and have an authorized service-and-repair facility located in California to perform warranty repairs.


  • Compliance extensions due to private financing, equipment manufacture delays, or installer delays may be granted for a maximum of six months (previously four months).

Other resources provided by CARB:

Fact sheet

TRU Information

TRUs developed to meet both CARB and EPA Emission compliance

Contact your local Thermo King Dealer to find out about our compliant Precedent Units.