Motor Vehicle Air Conditioning Refrigerant Transition & Environmental Impacts
Since 1994, the most common refrigerant used in motor vehicle air conditioner (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: air conditioning, refrigeration, foam-blowing, fire retardants, solvents, and aerosols. Like the ozone-depleting substances they replace, most HFCs are potent greenhouse gases. Use of the ozone-depleting refrigerant, chlorofluorocarbon (CFC)-12, in new MVACs ceased in the mid-1990s in the United States. Today, many motor vehicle manufacturers are beginning to transition to new, climate-friendly alternative refrigerants.
Significant New Alternatives Policy (SNAP) Program
EPA’s Significant New Alternatives Policy (SNAP) program, under section 612 of the Clean Air Act (CAA), ensures the smooth transition to alternatives that pose lower overall risk to human health and the environment. The SNAP program evaluates and finds acceptable substitutes for ozone-depleting substances. Under the SNAP program, EPA has found acceptable, subject to use conditions, three low global warming potential MVAC refrigerants: HFC-152a, hydrofluoroolefin (HFO)-1234yf, and carbon dioxide (CO2). None of these alternatives deplete the ozone layer and all have significantly lower global warming potentials than CFC-12 or HFC‑134a. Table 1 shows the relative global warming potential (GWP) of these MVAC refrigerants and whether or not they are ozone depleting. As of 2014, there are cars on the road that use CFC-12, HFC-134a, and HFO-1234yf. Technicians must be certified under Section 609 of the CAA by an EPA-approved technician training and certification program to service any MVAC, regardless of the refrigerant.
Retrofitting CFC-12 MVACs is also regulated under the SNAP program. See section below titled “Retrofitting CFC-12 Vehicles to Alternative Refrigerants”.
Environmental Impacts of MVAC Refrigerants
|Table 1. Environmental Impacts of MVAC Refrigerantsi,ii|
|MVAC Refrigerant||Global Warming Potential||Ozone Depleting?|
CFC-12: an Ozone-Depleting RefrigerantCFC-12, the refrigerant used in MVACs until the 1990s, is a Class I ozone depleting substance, which means that its release into the atmosphere results in the destruction of the ozone layer. The ozone layer is present 10 to 30 miles above the earth’s surface in the stratosphere, and it protect us from harmful ultraviolet (UV) radiation. When CFC-12 is present in the stratosphere, strong UV radiation breaks the CFC-12 molecules apart, releasing chlorine. A single chlorine atom can destroy over one hundred thousand ozone molecules. Ozone loss in the atmosphere results in higher levels of UVB reaching the Earth's surface and leads to negative health and environmental impacts. These impacts include increases in both cataracts and skin cancer, and ozone loss could weaken the human immune system. Agriculture, as well as plant and animal life, may also be 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.
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.
HFC-134a: a Potent Greenhouse Gas
HFC-134a has remained the most common refrigerant used in MVAC since the 1990s. Although HFC-134a does not deplete the ozone, it is a potent greenhouse gas (GHG) with a global warming potential that is 1,430 times greater than CO2. In the United States, emissions of HFCs are increasing more quickly than those of any other greenhouse gas, and globally they are increasing 10-15% annually. At that rate, emissions are projected to double by 2020 and triple by 2030. HFC-134a is the most abundant HFC in the atmosphere. Its use to motor vehicle air conditioners accounts for an estimated 24% of total global HFC consumption.1
New Climate-Friendly Alternative Refrigerants
As discussed above, EPA’s Significant New Alternatives Policy (SNAP) Program ensures the smooth transition from ozone depleting substances to alternatives that pose lower overall risk to human health and the environment. Under SNAP, EPA recently listed three low global warming potential (GWP) MVAC refrigerants as acceptable subject to use conditions: hydrofluoroolefin (HFO)-1234yf, carbon dioxide, and HFC‑152a. None of these alternatives deplete the ozone layer and all have significantly lower impacts to the climate system than CFC-12 or HFC‑134a.
In the United States and globally, many automobile manufacturers are transitioning to these low-GWP alternatives. It is important for both consumers and technicians to be aware of these alternative refrigerants, their properties, and proper servicing procedures. The Society of Automotive Engineers (SAE) International has developed SAE Ground Vehicle Standards on these alternative refrigerants. These standards, also known as SAE J Standards, are available at http://standards.sae.org.
- GWP of 4
- Acceptable subject to use conditions for new passenger cars and light-duty trucks only; final rule published March 29, 2011 (76 FR 17488)
- HFO‑1234yf is mildly flammable (ASHRAE A2L), but can be used safely
- There are cars on the road using HFO-1234yf and it is increasingly being adopted by automobile manufacturers
- Under the 2011 SNAP listing, EPA established the following
conditions for use:
- 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; final rule published 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
- Although CO2 is exempt from the Section 608 venting prohibition, CO2 is not exempt from the Section 609 requirement to properly use certified refrigerant handling equipment.
- Under the 2012 SNAP listing, EPA established the following
conditions of use:
- 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).
- GWP of 124
- SNAP listed as acceptable subject to use conditions for new vehicles only; final rule published June 12, 2008 (73 FR 33304)
- HFC-152a is moderately flammable (ASHRAE A2), but can be used safely
- May be pursued by automobile manufacturers in the future
- Under the 2008 SNAP listing, EPA established the following
conditions for use:
- 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.”
Retrofitting CFC-12 MVACs
The retrofitting of CFC-12 vehicles is also regulated under EPA’s SNAP program. SNAP requires that when retrofitting a CFC-12 vehicle for use with another refrigerant, the technician must extract the CFC-12, must cover the CFC-12 label with a label that indicates the new refrigerant in the system and other information, and must affix new fittings unique to that refrigerant. The label must include the name and address of the technician and the company performing the retrofit; the date of the retrofit; the trade name, charge amount, and, when applicable, the ASHRAE refrigerant numerical designation of the refrigerant; and the type, manufacturer, and amount of lubricant used. If the refrigerant is or contains an ozone-depleting substance, the label must state “ozone depleter”, and if the refrigerant is flammable, it must include the statement “This refrigerant is FLAMMABLE. Take appropriate precautions.” The label must be large enough to be easily read, must be permanent, and must be affixed to the system over information related to the previous refrigerant, in a location not normally replaced during vehicle repair. If information on the previous refrigerant cannot be covered by the new label, the original label must be permanently rendered unreadable. Lastly, the background color of the label must be unique to the refrigerant. This information is needed so that subsequent technicians working on the MVAC system will be able to service the system properly, decreasing the likelihood of significant refrigerant emissions, cross-contamination and potential failure of air conditioning systems and refrigerant recovery/recycling equipment.
CFC-12 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. There are no alternatives approved to retrofit HFC-134a systems.