A2L refrigerants: R-454B, R-32 and the R-410A phase-out explained

New residential AC and heat pump systems in the U.S. now ship with A2L refrigerants, mainly R-454B and R-32. R-410A isn't banned: existing systems can be serviced, and since a May 2026 rule, R-410A equipment made or imported before January 1, 2025 can still be installed until the inventory runs out. What changed for good is everything around a new install: the equipment listing, the code checklist, the tools, the cylinders and the price.

This guide explains what A2L means, how the refrigerants compare (including where sources disagree on GWP), the actual EPA timeline, a field checklist built from UL's code guidance, and how to price and talk about it with customers. Regulatory facts were checked against EPA, the Federal Register and the eCFR in October 2026. Where the rules are still moving, we say so.

What "A2L" means

ASHRAE Standard 34 gives each refrigerant a safety group: a letter for toxicity (A lower, B higher) and a number for flammability (1 no flame propagation, 2L lower flammability, 2 flammable, 3 higher flammability). The "L" subclass is for refrigerants whose burning velocity is under 10 centimeters per second; ACHR News reported R-32 at 6.7 cm/s and R-454B at 5.2 cm/s¹. In practice, A2Ls are hard to ignite and burn slowly, but a large enough leak meeting a strong enough ignition source in a confined space can burn. That's why A2L equipment, codes and tools carry safety requirements R-410A never needed.

EPA's SNAP listings for residential and light commercial AC show the classes side by side: R-410A is A1, R-32 and R-454B are A2L, and propane (R-290) is A3, acceptable only in self-contained room air conditioners².

R-454B vs R-32 vs R-410A

Why the GWP numbers differ. EPA's AIM Act rules calculate a blend's GWP by weighting each component: R-32 at 675, R-125 at 3,500, R-1234yf at 1⁴. That gives about 2,088 for R-410A and 465 for R-454B. EPA's own SNAP table rounds to 2,090 and 470, and refrigerant makers often publish 466 for R-454B. The difference doesn't matter for compliance (every A2L here is well under 700), but if a spec sheet and a regulation disagree, the regulation's method is the one that counts.

Which refrigerant you handle depends on the brand: manufacturers chose different refrigerants for their residential lines, so many shops now stock and service both. They are not interchangeable. Each system is designed, tested and certified for one refrigerant.

The EPA timeline: what's restricted and when

The restrictions come from the AIM Act's Technology Transitions program. The residential and light commercial rules have changed several times⁵:

1. October 2023

   Original Technology Transitions rule

   Restricts higher-GWP HFCs in new equipment across many sectors. Residential and light commercial AC and heat pumps: 700 GWP limit.

2. December 2023

   Interim final rule

   Systems using components made or imported before January 1, 2025 may be installed until January 1, 2026.

3. December 2024

   VRF rule

   New VRF above 700 GWP can be installed until January 1, 2027 if all components were made or imported before January 1, 2026; until January 1, 2028 with a building permit issued before October 5, 2023.

4. January 1, 2025

   700 limit takes effect

   Self-contained units (window, portable): manufacture and import. Split systems: installation, unless all specified components were made or imported before this date.

5. October 3, 2025

   Reconsideration proposed

   EPA proposes removing the January 1, 2026 installation deadline for pre-2025 equipment.

6. May 26, 2026

   Reconsideration final

   Removes the January 1, 2026 installation date for pre-2025 residential and light commercial systems, allowing that inventory to be installed until supply runs out. Also relaxes limits and timelines for supermarkets, remote condensing units and cold storage.

The May 2026 rule, signed May 21 and published May 26, says it allows pre-2025 inventory of AC systems to be installed until supply runs out⁶⁷. EPA's sector table, updated August 28, 2026, now shows split systems with a January 1, 2025 installation date and a footnote: no installation date applies where all specified components were manufactured or imported before January 1, 2025⁸.

R-410A for service, and why it will cost more

Technology Transitions doesn't restrict servicing existing systems. But R-410A is an HFC, and total HFC production and consumption is capped as a share of the historical baseline⁴:

The 2029 step halves the cap. Recovered and reclaimed R-410A will matter more, and from January 1, 2029 the AIM Act reclaim rule requires reclaimed refrigerant for servicing supermarket systems, refrigerated transport and automatic commercial ice makers (not residential AC)⁹. For a homeowner with an older R-410A system and a big leak, future refrigerant cost is a fair factor in a repair-or-replace conversation.

What changes on the install

The equipment listing and the code

A2L equipment is certified to UL 60335-2-40. EPA's SNAP use conditions for these refrigerants in residential AC currently reference the standard's 3rd edition; EPA proposed updating the use conditions in SNAP Proposed Rule 27 (November 2025), which EPA's page still shows as proposed, not final¹⁰. The 2024 International Residential Code, section M1411.2, requires A2L appliances to be certified to UL 60335-2-40 and installed per the manufacturer's instructions; the 2024 IMC and UMC have matching requirements¹¹¹².

UL Solutions publishes a free install checklist for each code. Here's the IRC 2024 version, condensed¹¹:

UL notes that RDS and minimum room size typically apply to equipment with more than about 2 pounds of charge for non-fixed factory-sealed units, or about 4 pounds for other equipment¹¹. For commercial work, the IMC and UMC checklist adds design to ASHRAE 15, effective dispersal volume calculations, pipe labeling ("WARNING – Risk of Fire. Flammable Refrigerant") and a limit on hot surfaces above 1,290°F in ductwork unless interlocked with airflow¹².

States and cities adopt code editions on their own schedules, often with amendments. Before your first A2L install in a jurisdiction, ask the building department which edition applies.

Tools

Anything that touches the refrigerant circuit, or could be an ignition source near a leak, should be rated for A2L: recovery machines, vacuum pumps (spark-free switching) and electronic leak detectors. Many manifolds and hoses work for both, but many shops keep separate A1 and A2L sets to avoid cross-contamination. Check the tool maker's listing, not just the box.

Cylinders

From ACCA's guidance¹³:

• Gray body, red band. Cylinders are now gray with the ASHRAE R-number. A2L cylinders must also carry a red band at the top, and the box carries a flammable placard.
• Left-hand threads. Most makers moved A2L cylinders to a left-hand thread (CGA 164) fitting. That's an AHRI guideline, not a legal requirement, so stock adapters.
• Relief valves, not rupture discs. A2L cylinders require resealable pressure relief valves. ACCA warns that non-compliant imported cylinders with rupture discs have shown up in the U.S. market. Buy from reputable suppliers.
• Storage. Relief valve in the vapor space, pointing up; never above 125°F, the maximum for any refrigerant cylinder.
• Smaller fills. Fill weights dropped from 30 to 20 pounds because shipping fill limits depend on refrigerant density.
• Heels. From January 1, 2028, used disposable cylinders must go to a reclaimer or a processor that removes the heel, or a certified tech evacuates the heel to 15 inches of mercury vacuum and signs a statement⁹.

Certification and training

EPA Section 608 already covers A2Ls: since January 1, 2018, certification applies to appliances containing any non-exempt substitute refrigerant¹⁴. As of October 2026 we found no separate federal A2L certification. Train every tech before they open their first A2L system anyway. Brazing, leak testing and charging follow each manufacturer's A2L procedures, and the code checklist above is new to most crews. See our EPA 608 guide for the rest of the refrigerant rules.

Pricing and customer conversations

The transition raised costs in several places at once: new equipment, refrigerant and cylinder supply (R-454B and especially 20-pound A2L cylinders were short at times in 2025, according to the ICC¹⁵), A2L-rated tools, training time, and longer installs while crews learn the RDS wiring, room-size checks and labeling. We don't publish "typical" increases because they vary by brand, region and distributor.

Instead, rebuild replacement prices from your actual costs:

Use actual hours from your last several A2L installs, not your R-410A install times. Our HVAC pricing guide covers the selling rate and margin math.

Talking to customers. Short, calm, accurate answers build trust:

• "Do I have to replace my R-410A system?" No. Existing systems can be serviced and repaired. The rules apply to new equipment.
• "Is the new refrigerant safe?" A2Ls are classified lower toxicity and lower flammability. The equipment is certified to a safety standard written for them, often with a leak sensor, and installers follow specific code requirements.
• "Will repairs on my old system get more expensive?" Possibly, as R-410A supply shrinks with the HFC cap. It's one factor in a repair-or-replace decision, alongside age, efficiency and repair history.
• "Should I buy an R-410A system while I can?" Pre-2025 R-410A equipment can still be installed legally. It may cost less up front and can be serviced for its life, but future refrigerant may cost more. Show it next to an A2L option and let the customer choose.

A good-better-best estimate is the natural place for that last conversation, with the refrigerant noted on each option. In TradesWork, equipment records keep refrigerant type, age and service history for every unit, so techs know whether they're walking into an R-22, R-410A, R-454B or R-32 home before they arrive, and every charge and recovery is logged per unit and per tech with the tech's EPA 608 number.

A2L transition checklist for owners

• Every tech trained on A2L handling and the code install checklist.
• A2L-rated recovery machine, vacuum pump and leak detector on every truck that installs or services A2L systems.
• Left-hand thread adapters and A2L recovery cylinders stocked; no rupture-disc cylinders.
• UL's code checklist printed for each crew, and installation manuals reviewed for each model you sell.
• Code edition and amendments confirmed with each building department you work in.
• Replacement prices rebuilt from current equipment costs and actual A2L install hours.
• CSRs and techs given the four customer answers above.
• Refrigerant type recorded on every equipment record.
• EPA's sector table checked at least twice a year.