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 new, climate-friendly alternative refrigerants. As a result of a July 2015 rulemaking, by model year 2021, the MVAC systems in newly manufactured light-duty vehicles in the United States will no longer use HFC-134a.

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. 

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 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 impacts. These impacts 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.  
• HFC-134a will no longer be approved for use in new light-duty vehicles manufactured or sold in the United States as of model year 2021 as a result of EPA’s July 2015 final rule under SNAP (July 20, 2015, 80 FR 42870).
  • Limited exemption (narrowed use limit) through MY 2025 for use of HFC-134a in vehicles destined for use in countries that do not have infrastructure in place for servicing with other acceptable refrigerants (July 20, 2015, 80 FR 42870).
  • Servicing of existing vehicles using HFC-134a with HFC-134a will not be impacted and will continue to be allowed.

New Climate-Friendly Alternative Refrigerants

In the United States and globally, many automobile manufacturers are transitioning to the lower-GWP alternatives approved by SNAP, described below. None of these deplete the ozone layer and all have significantly lower impacts on the climate system than HFC‑134a.

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)Exit 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.

HFO-1234yf (R-1234yf)

• GWP of 4
• Acceptable, subject to use conditions, for new passenger cars and light-duty trucks only (March 29, 2011, 76 FR 17488; March 26, 2012, 77 FR 17344)
• Mildly flammable (ASHRAE A2L), but can be used safely
• Models using HFO-1234yf include: Cadillac XTS, Chevrolet Spark EV, BMW i3 and i8, Chrysler 200, Chrysler 300, Dodge Challenger, Dodge Charger, Dodge Dart, Dodge Durango, Jeep Cherokee, Jeep Wrangler, Ram 1500, Fiat 500 and 500L, Alfa Romeo 4C, Honda Fit EV, Tesla Model S, Range Rover, and Range Rover Sport
• Required use conditions:
  • HFO-1234yf MVAC systems must adhere to all of the safety requirements of SAE J639 (adopted 2011), 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 (revised October 2011).
  • Manufacturers must conduct Failure Mode and Effect Analysis (FMEA) as provided in SAE J1739 (adopted 2009). Manufacturers must keep the FMEA on file for at least three years from the date of creation.

Carbon Dioxide (CO₂, R-744)

• 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 (EPA 2012b).

HFC-152a (R-152a)

• GWP of 124
• Acceptable, subject to use conditions, for new vehicles only (June 12, 2008, 73 FR 33304)
• 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.”