Acceptable Refrigerants and their Impacts

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Q&A on Hydrocarbon Safety for MVACs

Guidance for Technicians

Brochure on New Climate-Friendly MVAC Refrigerants

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Use of the ozone-depleting refrigerant, chlorofluorocarbon (CFC)-12, in new motor vehicle air conditioning (MVAC) systems ended in the mid-1990s in the United States. Since 1994, the most common refrigerant used in MVAC systems has been hydrofluorocarbon (HFC)-134a. HFCs are intentionally-made fluorinated greenhouse gases used in the same applications where ozone-depleting substances have been used, including motor vehicle air conditioning. Like the ozone-depleting substances they replace, most HFCs are potent greenhouse gases with very high global warming potentials (GWPs). In 2012, automobile manufacturers began the transition to lower-GWP refrigerants, such as HFO-1234yf in light-duty vehicles. HFCs and their substitutes in certain subsectors including MVACs are also regulated under the American Innovation and Manufacturing (AIM) Act.

Significant New Alternatives Policy (SNAP) Program

EPA’s Significant New Alternatives Policy (SNAP) program reviews substitutes within a comparative risk framework in a variety of industrial sectors that historically used ozone-depleting substances. MVAC systems are one end-use within the refrigeration and air conditioning sector. The SNAP program evaluates and lists substitutes that reduce overall risk to human health and the environment considering ozone-depletion potential, global warming potential (GWP), flammability, toxicity, local air quality, ecosystem effects, and occupational and consumer health/safety. SNAP lists substitutes as acceptable, acceptable subject to use conditions or unacceptable. MVAC refrigerants are listed as either acceptable subject to use conditions or unacceptable.

Retrofitting CFC-12 MVAC systems is also regulated under the SNAP program. Vehicles may only be retrofitted with alternatives approved under SNAP for use as retrofits. HFC-134a is the primary refrigerant currently used to retrofit CFC-12 systems. For additional information, visit Choosing and Using a Retrofit Refrigerants for a CFC-12 Motor Vehicle Air Conditioner.

Under SNAP, all flammable refrigerants, except HFC-152a and HFO-1234yf, are listed as unacceptable for use in new and retrofit MVAC systems. This includes all hydrocarbon refrigerants. When a refrigerant is listed as unacceptable, its use is illegal. 

Environmental Impacts of MVAC Refrigerants
MVAC Refrigerant Global Warming Potential Ozone Depleting?
CFC-12 10,900 Yes
HFC-134a 1,430 No
HFC-152a 124 No
HFO-1234yf 4 No
CO2  (R-744) 1 No

CFC-12: an Ozone-Depleting Refrigerant

  • Ozone depleting refrigerant with a GWP of 10,900
  • Automobile manufacturers began to transition to the non-ozone depleting refrigerant, HFC-134a, with 1992 model year vehicles. By the 1995 model year, all new vehicles sold in the United States with air conditioners used HFC-134a refrigerant. 

The ozone layer The region of the stratosphere containing the bulk of atmospheric ozone. The ozone layer lies approximately 15-40 kilometers (10-25 miles) above the Earth's surface, in the stratosphere. Depletion of this layer by ozone-depleting substances will lead to higher UVB levels (a band of ultraviolet radiation), which in turn will cause increased skin cancers and cataracts and potential damage to some marine organisms, plants, and plastics. is present 10 to 30 miles above the earth’s surface in the stratosphere where it protect us from harmful ultraviolet (UV) radiation. Ozone loss in the atmosphere allows higher levels of UVB to reach the Earth's surface and leads to negative health and environmental effects. These effects include increases in cataracts, skin cancer, and weakened immune systems. Plant and animal life, agriculture, and materials like plastics and paints are also affected. 

The stratospheric ozone layer should not be confused with ground-level ozone. Ozone is "good up high, bad nearby." Even though it protects us when it is in the stratosphere, ozone at ground level can be harmful to breathe and is a prime ingredient in smog. 

HFC-134a: a Potent Greenhouse Gas

  • Most common refrigerant used in MVAC systems since the 1990s.
  • Potent greenhouse gas with a global warming potential that is 1,430 times that of CO2.
  • Use of HFC-134a in MVAC systems accounts for an estimated 24% of total global HFC consumption. It is the most abundant HFC in the atmosphere.  
  • The restriction of HFC-134a will occur under a broader prohibition of any substances with a Global Warming Potential (GWP) higher than 150 in the MVAC sector.
    • HFC-134a will no longer be allowed in nonroad vehicles as of January 1, 2028.
    • Servicing of existing vehicles using HFC-134a with HFC-134a will not be impacted and will continue to be allowed.

Lower-GWP Refrigerants

The development of MVAC systems using lower-GWP refrigerants has been encouraged by MVAC refrigerant requirements in Europe, where the EU Directive on Mobile Air Conditioning (MAC Directive) mandates transition to a refrigerant with a GWP below 150 by January 1, 2017, and in the United States by the availability of credits under the MY 2017-2025 Light-Duty Greenhouse (LD GHG) Rule (77 FR 62624, October 15, 2012).

It is important for both consumers and technicians to be aware of these alternative refrigerants, their properties, and proper servicing procedures. A printable brochure is available for new climate-friendly motor vehicle air conditioning refrigerants. EPA’s regulatory requirements for the servicing of MVAC systems apply to all three of these refrigerants.

  • HFC-152a

    • GWP of 124
    • Moderately flammable (ASHRAE A2), but can be used safely.
    • May be pursued by automobile manufacturers in the future.
    • Required use conditions:
      • Engineering strategies and/or devices shall be incorporated into the system such that foreseeable leaks into the passenger compartment do not result in R-152a concentrations of 3.7% v/v or above in any part of the free space1 inside the passenger compartment for more than 15 seconds when the car ignition is on

    • Manufacturers must adhere to all the safety requirements listed in the SAE Standard J639, including unique fittings and a flammable refrigerant warning label as well as SAE Standard J2773, “Refrigerant Guidelines for Safety and Risk Analysis for Use in Mobile Air Conditioning Systems."

  • HFO-1234yf

    • GWP of 4
    • Currently used in the majority of light-duty vehicles. See EPA Automotive Trends Report. 
    • Acceptable, subject to use conditions, for new passenger cars and light-duty trucks (March 29, 2011, 76 FR 17488; March 26, 2012, 77 FR 17344), in medium-duty passenger vehicles, heavy-duty (HD) pickup trucks, and complete HD vans (December 1, 2016, 81 FR 86779), and certain nonroad vehicles (May 4, 2022, 87 FR 26276)
    • Mildly flammable (ASHRAE A2L) but can be used safely.
    • Required use conditions:
      • HFO-1234yf MVAC systems must adhere to all of the safety requirements of SAE J639, including requirements for a flammable refrigerant warning label, high-pressure compressor cutoff switch and pressure relief devices, and unique fittings. For connections with refrigerant containers for use in professional servicing, use fittings must be consistent with SAE J2844.
      • Manufacturers must conduct Failure Mode and Effect Analysis (FMEA) as provided in SAE J1739. Manufacturers must keep the FMEA on file for at least three years from the date of creation.

  • CO2 (R744)

    • GWP of 1
    • Acceptable, subject to use conditions, for new vehicles only (June 6, 2012, 77 FR 33315)
    • Operates at 5 to 10 times higher pressure than other MVAC systems.
    • Under development by several foreign automobile manufacturers
    • Exempt from the Section 608 venting prohibition, meaning it is legal to knowingly release this refrigerant to the environment; however, CO2 is not exempt from the Section 609 requirements such as use of certified refrigerant handling equipment.
    • Required use conditions:
      • Engineering strategies and/or mitigation devices shall be incorporated such that in the event of refrigerant leaks the resulting CO2 concentrations do not exceed the STEL of 30,000 ppm averaged over 15 minutes in the passenger free space and the ceiling limit of 40,000 ppm in the passenger breathing zone.
      • OEMs must keep records of the tests performed for a minimum period of three years demonstrating that CO2 refrigerant levels do not exceed the STEL of 30,000 ppm averaged over 15 minutes in the passenger free space, and the ceiling limit of 40,000 ppm in the breathing zone.
      • The use of CO2 in MVAC systems must adhere to the standard conditions identified in SAE Standard J639.

MVAC HFC Restrictions Under the Technology Transitions Program of the AIM Act

On October 24, 2023, EPA issued a final rule titled Phasedown of Hydrofluorocarbons: Restrictions on the Use of Certain Hydrofluorocarbons under the American Innovation and Manufacturing Act of 2020, to implement sector-based transitions through restrictions on higher-GWP HFCs in aerosol, foams, and RACHP (refrigeration, air conditioning, and heat pump) products and equipment. The rule restricts the use of HFCs with a GWP of 150 or greater (e.g., HFC-134a) in newly manufactured and imported light-duty vehicles, medium-duty passenger vehicles, heavy-duty pick-up trucks, complete heavy-duty vans, and certain nonroad vehicles. See Technology Transitions final rule. This final rule does not affect existing MVACs so existing vehicles can continue to be serviced with HFC-134a and other refrigerants with a GWP of 150 or greater. The following table summarizes requirements of this final rule for newly manufactured vehicles.

HFC Restrictions for MVACS in Newly Manufactured Vehicles in the October 2023 Technology Transitions final rule
Types of Vehicles Global Warming Potential Limit for Refrigerant Affected Model Years (including imports) and Compliance Date Servicing Requirements
Light-duty passenger vehicles 150 Model Year 2025, and no earlier than October 24, 2024 Existing vehicles can continue to be serviced with HFC-134a and other refrigerants with a GWP of 150 or greater.
Medium-duty passenger vehicles, heavy-duty pick-up trucks, complete heavy-duty vans 150 Model Year 2028 Existing vehicles can continue to be serviced with HFC-134a and other refrigerants with a GWP of 150 or greater.
Listed nonroad vehicles (agricultural tractors greater than 40 horsepower; self-propelled agricultural machinery; compact equipment; construction, forestry, and mining equipment; and commercial utility vehicles) 150 January 1, 2028 Existing vehicles can continue to be serviced with HFC-134a and other refrigerants with a GWP of 150 or greater.

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Last updated on August 16, 2024