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Federal Register / Vol. 86, No. 86 / Thursday, May 6, 2021 / Rules and Regulations
included in the UL Standard that is adopted as a use condition in these final SNAP listings. Nonetheless, we find that these A2L refrigerants can be used safely provided the use conditions in this rule are followed, including compliance with the requirements of the UL Standard. In certain clauses, the UL
Standard requires compliance with ASHRAE 15. We also note that other authorities might impose additional requirements, such as adoption of ASHRAE 15 and 15.2 in building codes, that would provide an additional layer of safety above what EPA is requiring.
If in the future EPA were to determine that additional requirements are needed after this rulemaking to ensure safe use of the refrigerants in the residential and light commercial AC and heat pumps end-use, EPA could consider any relevant changes and if any revisions to this final rule should be proposed.
Comment: The Alliance noted that the standard proposed to be incorporated by reference, UL 60335240, 3rd edition, will likely be updated again. Daikin noted the standard is a continuous maintenance standard supporting reference to the current edition. AHRI
also pointed out that new and updated standards will become more important as standards sunset in the coming years. The Alliance expected the fourth edition soon, and forecasted that most products manufactured to this standard with the six A2L refrigerants would likely be certified to that fourth edition.
They asked that the UL 60355240
sic standard update to include refrigerants that meet all the requirements listed in the fourth edition as well. More generally they asked that references to the standards be updated as new editions become available for the products listed in SNAP Rule 23 and other rules. Carrier also suggested EPA
align with new safety standards as new editions and future revisions become available and Chemours offered similar suggestions. Sporlan and Trane suggested the use condition reference the latest edition of the UL Standard, such that the reference remains up to date. Sporlan suggested this use condition be modified to reference the latest released edition of this same standard, instead of tying Rule 23
exclusively to the 3rd Edition. Trane noted that future editions of the UL
Standard are already underway and predicted the fourth edition would be complete within two years i.e., by July 27, 2022. Honeywell also supported referencing a 4th edition and indicated that the process for writing such would start in August 2020 and expected completion in 2021. Honeywell asked
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EPA to wait until the 4th edition is published before finalizing these listings of the A2L refrigerants and noted that the 3rd edition does not cover mitigation measures for external fires caused by refrigerant leaks. AHRI also pointed out that there is an ongoing effort to harmonize the relevant safety standards and recommended that EPA
update references to requirements for compliance with product safety standards as new editions and revisions become available. Referencing both the third and fourth edition of UL 60335
240 as well as ASHRAE 152019 and the proposed ASHRAE 15.2, Johnson Controls called for the acceptability listing of these A2L refrigerants to be contingent upon the completion and harmonization of the governing UL and ASHRAE standards for the safe design and application of stationary air conditioning. Honeywell made a similar point, referencing ASHRAE
Standards 15 and 15.2, and suggested that these A2L listings be delayed until this harmonization process was complete.
Response: EPA acknowledges the information on further developments in the UL 60335240 standard and ASHRAE standards processes. After considering all the public comments on this proposal, we are finalizing this listing, as described in section II.B. EPA
is incorporating by reference the 3rd edition of the UL standard the existing version of the standard. As addressed below, we conclude, and several commenters agree, that this version adequately addresses the use of these A2L refrigerants in the equipment proposed.
As we noted above, in certain cases the UL Standard refers to ASHRAE 15
2019 for compliance. We are not, however, providing a use condition based on one or more future editions of this standard, nor do we feel it necessary or appropriate to rely on future standards and harmonization efforts. Not only does EPA not know exactly what these future standards may entail, those commenting on the proposed rule have not had the opportunity to review those updates, as they have not yet been finalized.
Similarly, we do not find it necessary or appropriate to wait for such actions to be finalized before taking this action.
The third edition of the UL Standard included extensive revisions specifically to address flammability risks of A2L refrigerants and reach industry-wide consensus. We further note that Chemours comments on the 2020 NPRM called finalization of this rule critical and timely and stated that with this final rule, the HVAC

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industry is now well prepared to take this important step forward in the use of lower-GWPand lower overall risk to human health and the environment refrigerants in this end-use. If and when a 4th edition of the UL Standard is released, EPA can consider any relevant changes and if any revisions to this final rule should be proposed.
Further, as mentioned by AHRI and Daikin, the UL standards are under continuous maintenanceas are ASHRAE Standards 15 and 15.2and hence may change again even after the mentioned editions are published.
Nonetheless, most commenters supported moving forward with the rule using the third edition of the UL
Standard. Daikin, for instance, endorses EPAs determination that this consensus safety standard adequately protects against the reasonably foreseeable risks associated with the use of R32 in the applications being considered. Chemours added that application and product standards for the end-uses referenced in the proposed rule are complete and that these updated standards sufficiently address the risks associated with the use of A2L
solutions. EPA concludes that reliance on the current UL Standard and our other use conditions allows applicable products to be used safely.
Regarding Honeywells comment on external fires, we note that a leak, even of a flammable refrigerant, does not cause a fire. It would require an ignition source and a concentration of the refrigerant higher than the lower flammability limit and below the higher flammability limit. Requirements in the UL Standard mitigate the risk of the equipment serving as an ignition source.
As noted above, AHRI pointed out that for almost all applications air circulation will be sufficient to dilute the refrigerant concentration in the event of a catastrophic leak to below 25% of the LFL. Only in a rare case will ventilation be used to introduce outside air. Further, the industry is actively studying the behavior of A2L
refrigerants presuming a leak does occur in a structural fire. Should the results of this research or other information lead in the future EPA to determine that additional requirements are needed after this rulemaking to ensure safe use of the refrigerants in the residential and light commercial AC and heat pumps end-use, EPA could consider any relevant changes and if any revisions to this final rule should be proposed.
We understand that the Alliance is asking EPA to modify the use condition so that it requires adherence to the fourth edition once the fourth edition
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