EPA 609 substitute refrigerants (SNAP)
This page covers EPA's Significant New Alternatives Policy (SNAP) program in 40 CFR Part 82, Subpart G, as it applies to motor vehicle air conditioning: what SNAP is, its prohibitions, the MVAC refrigerants listed as acceptable subject to use conditions, and those listed as unacceptable. In the SNAP tables, the Conditions column holds legal requirements and the Comments column holds EPA's remarks, which are not requirements; each point says which one it is. Each point quotes the rule and links to it.
The short answer
Under SNAP (40 CFR Part 82, Subpart G), no person may use a substitute without adhering to the use restrictions set by its acceptability decision, or after the effective date of a rule listing it as unacceptable. For new CFC-12 automobile motor vehicle air conditioning, Appendix B lists R-152a, HFO-1234yf and carbon dioxide as acceptable subject to use conditions, each with its own scope.
Each part of this answer is quoted from the rule below.
What SNAP is
Subpart G implements section 612 of the Clean Air Act, on the safe alternatives policy for the acceptability of substitutes for ozone-depleting compounds.
“The purpose of these regulations in this subpart is to implement section 612 of the Clean Air Act, as amended, regarding the safe alternatives policy on the acceptability of substitutes for ozone-depleting compounds.”
The program is called the Significant New Alternatives Policy, or SNAP, program.
“This program will henceforth be referred to as the “Significant New Alternatives Policy” (SNAP) program.”
A substitute (or alternative) is any chemical, product substitute or alternative manufacturing process, existing or new, intended to replace a class I or class II compound.
“Substitute or alternative means any chemical, product substitute, or alternative manufacturing process, whether existing or new, intended for use as a replacement for a class I or II compound.”
Use restrictions are either conditions on how a substitute can be used across a sector end-use, or limits on the end-uses or specific applications where it can be used.
“Use restrictions means restrictions on the use of a substitute imposing either conditions on how the substitute can be used across a sector end-use or limits on the end-uses or specific applications where it can be used within a sector.”
The rules also prohibit the use of alternatives that EPA has determined may have adverse effects on human health or the environment, where EPA has identified alternatives in that use sector that reduce overall risk and are currently or potentially available.
“Finally, the regulations prohibit the use of alternatives which EPA has determined may have adverse effects on human health or the environment where EPA has identified alternatives in particular industrial use sectors that on an overall basis, reduce risk to human health and the environment and are currently or potentially available.”
The SNAP prohibitions and listing decisions
No person may use a substitute without following the use restrictions set by its acceptability decision, once the rule imposing them has taken effect.
“(c) No person may use a substitute without adhering to any use restrictions set by the acceptability decision, after the effective date of any rulemaking imposing such restrictions.”
No person may use a substitute after the effective date of a rule adding it to the list of unacceptable substitutes.
“(d) No person may use a substitute after the effective date of any rulemaking adding such substitute to the list of unacceptable substitutes.”
“Acceptable subject to use conditions” means EPA found a substitute acceptable only if conditions of use are met to minimize risks to human health and the environment.
“(2) Acceptable subject to use conditions. After reviewing a notice, the Agency may make a determination that a substitute is acceptable only if conditions of use are met to minimize risks to human health and the environment.”
Using such a substitute in a way that does not follow its use conditions makes it unacceptable.
“Use of such substitutes in ways that are inconsistent with such use conditions renders them unacceptable.”
For a substitute “acceptable subject to narrowed use limits”, users intending to adopt it must ascertain that other alternatives are not technically feasible, and companies must document the results of their evaluation and keep them on file to demonstrate compliance.
“Users intending to adopt a substitute acceptable with narrowed use limits must ascertain that other alternatives are not technically feasible. Companies must document the results of their evaluation, and retain the results on file for the purpose of demonstrating compliance.”
“Unacceptable” applies where EPA's review shows the substitute poses a risk of adverse effects to human health and the environment and other alternatives exist that reduce overall risk.
“(4) Unacceptable. This designation will apply to substitutes where the Agency's review indicates that the substitute poses risk of adverse effects to human health and the environment and that other alternatives exist that reduce overall risk.”
MVAC substitutes acceptable subject to use conditions
For retrofitting CFC-12 automobile MVACs (retrofit equipment only), Appendix B's listing of HFC-134a, R-401C and HCFC Blend Beta (R-416A) requires that all CFC-12 be removed from the system before retrofitting.
“—all CFC-12 must be removed from the system prior to retrofitting”
Appendix B lists R-152a as acceptable subject to use conditions for CFC-12 automobile motor vehicle air conditioning, new equipment only. One condition: engineering strategies and/or devices must be built into the system so that foreseeable leaks into the passenger compartment do not cause R-152a concentrations of 3.7% v/v or more in any part of the free space inside the passenger compartment for more than 15 seconds while the ignition is on.
“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 space1inside the passenger compartment for more than 15 seconds when the car ignition is on”
Appendix B lists carbon dioxide (CO2) as acceptable subject to use conditions as a substitute for CFC-12 in motor vehicle air conditioning, new equipment only.
“CFC-12 Motor Vehicle Air Conditioning (New equipment only) Carbon dioxide (CO2) as a substitute for CFC-12”
A CO2 condition requires that, in the event of refrigerant leaks, the resulting CO2 concentrations do not exceed set limits.
“incorporated such that in the event of refrigerant leaks, the resulting CO2 concentrations do not exceed:”
Those limits are a short-term exposure level (STEL) of 3% (30,000 ppm) averaged over 15 minutes in the passenger free space, and a ceiling of 4% (40,000 ppm) in the passenger breathing zone.
“The short term exposure level (STEL) of 3% or 30,000 ppm averaged over 15 minutes in the passenger free space 1; and; The ceiling limit of 4% or 40,000 ppm in the passenger breathing zone. 2”
The CO2 conditions require vehicle manufacturers to keep records of the tests they performed.
“Vehicle manufacturers must keep records of the tests performed for a minimum”
The records must be kept for at least three years and must show that CO2 levels do not exceed the 3% STEL (15-minute average) in the passenger free space and the 4% ceiling in the breathing zone.
“period of three years demonstrating that CO2 refrigerant levels do not exceed the STEL of 3% averaged over 15 minutes in the passenger free space, and the ceiling limit of 4% in the breathing zone”
HFO-1234yf: scope and conditions
Appendix B lists HFO-1234yf as acceptable subject to use conditions as a substitute for CFC-12 in automobile motor vehicle air conditioning, for new equipment in passenger cars and light-duty trucks only.
“CFC-12 Automobile Motor Vehicle Air Conditioning (New equipment in passenger cars and light-duty trucks only)”
Appendix B has a separate HFO-1234yf listing for motor vehicle air conditioning, acceptable subject to use conditions, whose application is limited to newly manufactured medium-duty passenger vehicles.
“(newly manufactured medium-duty passenger vehicles)”
Appendix B has a separate HFO-1234yf listing for motor vehicle air conditioning, acceptable subject to use conditions, whose application is limited to newly manufactured heavy-duty pickup trucks.
“(newly manufactured heavy-duty pickup trucks)”
Appendix B has a separate HFO-1234yf listing for motor vehicle air conditioning, acceptable subject to use conditions, whose application is limited to newly manufactured complete heavy-duty vans only.
“(newly manufactured complete heavy-duty vans only)”
EPA's comments in the table (not a condition) say complete heavy-duty vans are not altered by a secondary or tertiary manufacturer.
“Complete heavy-duty vans are not altered by a secondary or tertiary manufacturer.”
Appendix B has a separate HFO-1234yf listing for motor vehicle air conditioning, acceptable subject to use conditions, whose application is limited to newly manufactured nonroad agricultural tractors with greater than 40 horsepower.
“(newly manufactured nonroad agricultural tractors with greater than 40 horsepower)”
As of June 3, 2022, the HFO-1234yf conditions require HFO-1234yf MVAC systems to adhere to all of the safety requirements of SAE J639, including requirements for a flammable refrigerant warning label, a high-pressure compressor cutoff switch and pressure relief devices, and unique fittings.
“As of June 3, 2022: (1) HFO-1234yf MVAC systems must adhere to all of the safety requirements of SAE J639,4 7 including requirements for a flammable refrigerant warning label, high-pressure compressor cutoff switch and pressure relief devices, and unique fittings.”
The second HFO-1234yf condition binds manufacturers: they must conduct a failure mode and effect analysis (FMEA) as provided in SAE J1739 and keep it on file for at least three years from its creation.
“(2) Manufacturers must conduct Failure Mode and Effect Analysis (FMEA) as provided in SAE J1739.5 7 Manufacturers must keep the FMEA on file for at least three years from the date of creation”
EPA's comments in the table (not a SNAP condition) note that, under EPA's Significant New Use Rule for HFO-1234yf under the Toxic Substances Control Act, commercial users or consumers can only recharge MVAC systems with HFO-1234yf where the original equipment manufacturer did the original charging with HFO-1234yf.
“Consistent with EPA's Significant New Use Rule for HFO-1234yf under the Toxic Substances Control Act, commercial users or consumers can only recharge MVAC systems with HFO-1234yf where the original charging of the system with HFO-1234yf was done by the original equipment manufacturer.”
Unacceptable MVAC substitutes
For CFC-12 motor vehicle air conditioners (retrofit and new equipment/NIKs), Appendix B lists flammable substitutes as unacceptable, other than R-152a or HFO-1234yf in new equipment.
“Flammable Substitutes, other than R-152a or HFO-1234yf in new equipment”
EPA's comments in the table (not a condition) say the risks of using flammable substitutes other than R-152a and HFO-1234yf in this end-use have not been addressed by a risk assessment, and that R-152a and HFO-1234yf may be used in new equipment with the use conditions in Appendix B.
“The risks associated with using flammable substitutes (except R-152a and HFO-1234yf) in this end-use have not been addressed by a risk assessment. R-152a and HFO-1234yf may be used in new equipment with the use conditions in appendix B to this subpart.”
Appendix B lists these refrigerants as unacceptable in motor vehicle air conditioning (new equipment in passenger cars and light-duty trucks only) as of Model Year 2017: R-406A, R-414A, R-414B, HCFC Blend Delta, Freeze 12, GHG-X5, HCFC Blend Lambda and R-416A.
“R-406A, R-414A (HCFC Blend Xi, GHG-X4), R-414B (HCFC Blend Omicron), HCFC Blend Delta (Free Zone), Freeze 12, GHG-X5, HCFC Blend Lambda (GHG-HP), R-416A (FRIGC FR-12, HCFC Blend Beta)”
EPA's comments on that listing (not a condition) note that these refrigerants all contain HCFCs.
“These refrigerants all contain HCFCs.”
Appendix B lists R-405A as unacceptable for CFC-12 motor vehicle air conditioners, both retrofit and new equipment/NIKs.
“CFC-12 R-405A Motor Vehicle Air Conditioners (Retrofit and New Equipment/ NIKs)”
Not covered here
We do not list every SNAP entry here. Appendix B also lists HFO-1234yf, subject to the same kind of conditions, for further newly manufactured nonroad equipment (such as self-propelled agricultural machinery, compact equipment, construction, forestry and mining equipment, and commercial utility vehicles), and other appendices of Subpart G list more substitutes; we cover only MVAC entries whose wording we could quote cleanly. We only write what an official source states, so study these parts with your certifying program's materials.
Sources
- eCFR: 40 CFR 82.170, Purpose and scope (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 40 CFR 82.172, Definitions (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 40 CFR 82.174, Prohibitions (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 40 CFR 82.180, Agency review of SNAP submissions (as of Nov 3, 2026)Checked November 5, 2026
- eCFR: 40 CFR Part 82, Subpart G, Appendix B (as of Nov 3, 2026)Checked November 5, 2026