The U.S. Environmental Protection Agency (EPA) has proposed Significant New Alternatives Policy (SNAP) Rule 27, which would list several substitute refrigerants as acceptable, subject to use conditions, for residential and light commercial air conditioners and heat pumps, chillers, household refrigerators and freezers, motor vehicle air conditioners, and fire suppression and explosion protection. This action also proposes to update use conditions for substitutes previously listed for certain air conditioning end uses, and for water coolers.
The proposal, issued October 24, reflects the EPA’s continuing effort under the SNAP program to support the transition toward lower-emission refrigerants while maintaining safety and performance standards.
Specifically, SNAP Rule 27 would:
- Update existing use conditions for R-32, R-452B, R-454A, R-454B, R-454C, R-457A, R-290, and R-441A in residential and light commercial air conditioners and heat pumps;
- List the hydrocarbon refrigerant (HCR) blend HCR 4141, HFO-1234ze(E), and the HFO/HFC blend R-516A as acceptable, subject to use conditions, in residential and light commercial air conditioning and heat pumps;
- List HCR 4141 as acceptable, subject to use conditions, in household refrigerators and freezers;
- Update existing use conditions for R-290 in water coolers; and
- List R-516A as acceptable, subject to use conditions, in positive displacement chillers and centrifugal chillers.
For some proposed listings in the refrigeration and air conditioning sector, EPA is proposing two options for a use condition. The first would require equipment meet all the requirements listed in the most recent edition, as of August 2025, of the Underwriters Laboratories (UL) standard for the end use, while the second would require equipment to be certified by an Occupational Safety and Health Administration (OSHA) Nationally Recognized Testing Laboratory (NRTL).
TABLE 1. Acceptable Alternatives with Use Conditions
| End Uses | Substitutes | Condition1 |
| Residential and Light Commercial AC and Heat Pumps (New) | HCR 4141, HFO-1234ze(E), R-516 | Acceptable Subject to Use Conditions2 |
| Household Refrigerators and Freezers (New) | HCR 4141 | Acceptable Subject to Use Conditions3 |
| Positive Displacement and Centrifugal Chillers (New) | R-516A | Acceptable Subject to Use Conditions |
1 For specific use conditions for substitutes listed as Acceptable Subject to Use Conditions, consult the proposed rule.
2 The EPA is taking comment on whether to finalize either: a use condition which would require use consistent with UL Standard 60335-2-40, 4th edition, or a use condition which would require certification by an NRTL.
3 EPA is taking comments on whether to finalize either: a use condition which would require use consistent with UL Standard 60335-2-24, 3rd edition, or a use condition which would require certification by an NRTL.
TABLE 2. Acceptable Alternatives with Updated Use Conditions
| End Uses | Substitutes | Condition1 |
| Residential and Light Commercial AC and Heat Pumps (New) | HFC-32, R-452B, R-454A, R-454B, R-454C, R-457A, R-290, R-441A | Acceptable only for use in new equipment2specifically designed for the refrigerant. Hazard markings and labels required. EPA is taking comment on whether to finalize either: a use condition which would require use consistent with UL Standard 60335-2-40, 4th edition, or a use condition which would require certification by an NRTL. |
| Water Coolers (New) | R-290 | Acceptable only for use in new equipment2 specifically designed for the refrigerant. Hazard markings and labels required. EPA is taking comment on whether to finalize either: a use condition which would require use consistent with UL Standard 399, 8th edition, or a use condition which would require certification by an NRTL. |
1 For specific use conditions, consult the proposed rule.
2 Applies to new equipment manufactured after the effective date of a final rule based on this proposal. Equipment manufactured between the effective date of the final rule and up to two years after the effective date of the final rule may follow either existing use conditions or the proposed updated use conditions. Consult the proposed rule for details.
Under the Clean Air Act (CAA) section 612, EPA’s SNAP program reviews substitutes in a comparative risk framework. EPA lists these substitutes as acceptable, acceptable subject to use conditions, acceptable subject to narrowed use limits, or unacceptable (prohibited) for specific uses. Section 612 requires EPA to list as acceptable those substitutes that do not present a significantly greater risk to human health and the environment as compared with other substitutes that are currently or potentially available.
EPA will accept public comments on the proposed SNAP Rule 27 for 45 days after publication of the proposal in the Federal Register. To submit a comment, identify it with Docket ID No. EPA-HQ-OAR-2024-0503 and follow the online instructions at www.regulations.gov.
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