A2L refrigerants and the EPA 608 exam: what the rules require, and what they do not

Checked on September 14, 2026, against the current eCFR text of 40 CFR 82.154 and 82.161, EPA's SNAP listing rule of May 6, 2021, EPA's SNAP substitutes page and Technology Transitions page, and EPA's Section 608 test-topic outline. Every figure below names its source; the sources are listed at the end.

New residential and light commercial air conditioners are shipping with R-32 and R-454B instead of R-410A, and both carry the safety class A2L. That label raises two practical questions for anyone studying for the Section 608 exam: what do the rules say about handling these refrigerants, and how much of it can the exam ask? This page answers both from the regulations and EPA's own pages, and it says plainly where the rules stop.

What A2L means

The safety classes come from ASHRAE Standard 34. EPA's 2021 listing rule spells out the 2019 edition's criteria. Class A means no toxicity was identified at concentrations of 400 parts per million or less. Class 2L means the refrigerant does propagate a flame when tested, but with a heat of combustion below 19,000 kJ/kg, a lower flammability limit above 0.10 kg/m3, and a maximum burning velocity of 10 cm/s or less in dry air at 73.4 degrees F. ASHRAE's name for the 2L class is "lower flammability", lower than classes 2 and 3 (EPA, SNAP Rule 23, section II.B.3 and II.B.4).

One wording point that matters when you read labels: EPA proposed to call these refrigerants "mildly flammable", then dropped the phrase in the final rule after comments, because it is not the term ASHRAE uses. The required warning labels use the words Warning, Risk of Fire, Flammable Refrigerant Used (EPA, SNAP Rule 23, section II.B and II.B.1.c).

For comparison, R-410A is class A1 with a global warming potential of 2,090. R-32 is A2L with a GWP of 675. R-454B is A2L with a GWP of 470, and it is a blend of 68.9 percent R-32 and 31.1 percent R-1234yf. Four more A2L blends are listed for the same equipment: R-452B (GWP 700), R-454A (240), R-454C (150) and R-457A (140) (EPA, SNAP substitutes page; EPA, SNAP Rule 23, section II.B.4).

Why they are in new equipment now

EPA's Technology Transitions rules under the AIM Act set a GWP limit of 700 for new residential and light commercial air conditioning and heat pump systems, with a compliance date of January 1, 2025. R-410A is above that limit; R-32 and R-454B are below it. Self-contained products in the same subsector, such as window and portable units, carry the same 700 limit for manufacture and import from January 1, 2025, and their sale is prohibited three years after that date. Variable refrigerant flow systems have a later date, January 1, 2027 (EPA, Technology Transitions HFC Restrictions by Sector).

Two details from the same page keep the picture honest. First, after EPA's 2026 reconsideration rule there is no installation deadline for residential and light commercial systems whose components were all manufactured or imported before January 1, 2025, so pre-2025 R-410A equipment can still be installed until that inventory runs out. Second, the restrictions are on new systems; components used to repair existing systems are not restricted, so R-410A service work continues (EPA, Technology Transitions HFC Restrictions by Sector, footnotes 5 and 6).

What the SNAP listing requires when A2Ls are used

Under the Significant New Alternatives Policy program, R-32, R-452B, R-454A, R-454B, R-454C and R-457A are acceptable in residential and light commercial air conditioning and heat pumps subject to use conditions (EPA, SNAP substitutes page). The 2021 rule that listed them sets those conditions:

• New equipment only. None of the six is listed as a retrofit refrigerant for existing equipment, because equipment designed for a nonflammable refrigerant can contain ignition sources. Existing tubing can be inspected and reused; the rest of the system must be new (EPA, SNAP Rule 23, section II.B.1.b).
• The equipment must meet the UL 60335-2-40 safety standard edition named in the listing, which covers charge sizes, ventilation, room-area requirements, warnings and markings (EPA, SNAP Rule 23, section II.B.1.a).
• Permanent warning labels in letters at least a quarter inch high, including the risk-of-fire and flammable-refrigerant warning on the outside of the unit and a minimum-room-area marking on the indoor unit (EPA, SNAP Rule 23, section II.B.1.c).
• Red-marked service ports, pipes and hoses, in Pantone 185 or RAL 3020, extending at least one inch, replaced if removed (EPA, SNAP Rule 23, section II.B.1.d).

The same rule states that knowingly venting these six refrigerants during service or disposal is prohibited under section 608(c)(2) of the Clean Air Act and 40 CFR 82.154(a)(1), and it notes that flammable refrigerant recovered from this equipment is likely hazardous waste under RCRA (EPA, SNAP Rule 23, sections II.B.1.d and II.B.4).

What Section 608 says about A2Ls

Section 608's rules do not mention A2L by name. They work through a single test: is the refrigerant a class I or class II substance, or a substitute that EPA has not exempted? The exempt list in 40 CFR 82.154(a)(1) covers carbon dioxide, nitrogen, water, ammonia in listed uses, chlorine in one industrial use, hydrocarbons in listed uses, ethane, propane, isobutane and R-441A in listed equipment. HFC and HFO blends are not on it. So for R-32, R-454B and the other A2L blends:

• Venting is prohibited, and knowingly releasing recovered refrigerant is a violation (§82.154(a)(1) and (a)(3)).
• No one may service or dispose of an appliance containing them without following the required practices and using recovery equipment certified for that refrigerant and appliance (§82.154(b)).
• Since January 1, 2018, they can only be sold to a certified technician, an employer of one, or the other listed buyers (§82.154(c)(1)).
• Since January 1, 2018, anyone who could reasonably be expected to break into the refrigerant circuit while servicing an appliance that contains a non-exempt substitute must hold a Section 608 certification (§82.161, opening paragraph and (a)(1)).

What Section 608 does not do is add a flammability credential. Neither §82.161 nor the exam standards in Appendix D name A2Ls or flammability classes. There is no separate federal A2L certification for stationary equipment; the certification is the same Type I, II, III or Universal card.

One more boundary worth knowing. The leak repair rules do not reach a typical home system. Section 608's leak repair section applies only to appliances with 50 or more pounds of an ozone-depleting refrigerant, and the AIM Act's leak repair rule excludes the residential and light commercial air conditioning and heat pump subsector (§82.157(a); §84.106(a)(3)(ii)). The venting prohibition and the certification requirement apply regardless of size.

What the exam can ask

EPA's published test-topic outline, last updated December 5, 2025, does not contain the term A2L or any flammability class. The nearest items are in the Core section: the venting prohibition on substitute refrigerants, the absence of drop-in replacements, lubricant incompatibility, the fractionation problem with blends, and the safety items on nitrogen rather than oxygen or compressed air for leak testing and on not filling cylinders past 80 percent. Type II adds that hydrocarbons are not approved for retrofits (EPA, Test Topics).

Read that as follows. The exam tests the framework: substitutes are covered by the venting prohibition, blends fractionate, retrofits need compatible lubricants and no drop-ins, and class 3 refrigerants such as propane are unacceptable for retrofitting split systems (EPA, SNAP substitutes page, note on class 3 refrigerants). It does not test A2L charge limits, leak detection response, or the UL standard. That knowledge comes from the equipment manufacturer's instructions and from training outside the Section 608 program, which EPA does not review or approve (EPA, Certification Programs for Section 608 Technicians). Whether your employer or your local authority requires such training is a separate question from the federal certification.

Numbers to remember

• A2L: class A, no toxicity identified at 400 ppm or less; class 2L, flame propagation with heat of combustion under 19,000 kJ/kg, LFL above 0.10 kg/m3, burning velocity 10 cm/s or less
• The regulation's word is "flammable", not "mildly flammable"
• R-410A: A1, GWP 2,090. R-32: A2L, GWP 675. R-454B: A2L, GWP 470, 68.9 percent R-32 and 31.1 percent R-1234yf
• Technology Transitions: 700 GWP limit for new residential and light commercial systems, compliance date January 1, 2025; no installation deadline for all-pre-2025 components; repair components not restricted; VRF January 1, 2027
• SNAP use conditions: new equipment only, no retrofits; UL 60335-2-40; quarter-inch warning labels; red-marked service ports
• Section 608: A2L blends are non-exempt substitutes, so no venting, certified recovery equipment, sales only to certified buyers since 2018, and Section 608 certification required since 2018
• No separate federal A2L certification; the outline does not mention A2L

If you want the framework questions drilled until they are automatic, the EPA 608 Prep app covers the venting prohibition, substitutes, blends and retrofit rules with sourced explanations: EPA 608 Prep: HVAC Tests 2026.

This article is a study aid, not compliance advice. For the binding text, use the eCFR links above. StudyRig is an independent publisher and is not affiliated with or endorsed by the U.S. Environmental Protection Agency or any certification provider.