What is A2L refrigerant?

If you've opened a new residential condenser since 2025, you've probably seen "A2L" on the nameplate and a red band on the refrigerant cylinder. The label is a safety rating, and it tells you two things about the refrigerant inside: how toxic it is and how easily it burns. This page explains the rating, lists the refrigerants that carry it and covers what it changes on a service call. For the full install checklist, cylinder rules and pricing advice, see our A2L refrigerants guide.

What does A2L mean?

ASHRAE Standard 34 gives every refrigerant a safety group made of a letter and a number¹. The letter is toxicity: A is lower toxicity, B is higher. The number is flammability: 1 shows no flame propagation in the standard test, 2L is lower flammability, 2 is flammable and 3 is higher flammability. Put them together and you get groups like A1 (R-410A, R-22), A2L (R-32, R-454B) and A3 (propane, R-290).

2L started as an optional subclass of Class 2. ASHRAE's Addendum g to Standard 34-2016, approved in June 2018, made it a class of its own¹.

How does a refrigerant qualify as Class 2L?

Under Addendum g, a single-compound refrigerant is Class 2L only if it meets all four conditions¹. Blends must pass them as formulated and in their worst-case fractionated state.

1. 1

   It propagates a flame

   When tested at 60°C (140°F) and 101.3 kPa, a flame spreads. If it doesn't, the refrigerant is Class 1.

2. 2

   Its lower flammability limit is above 0.10 kg/m³

   It takes a fairly high concentration in air before it can burn at all.

3. 3

   Its heat of combustion is under 19,000 kJ/kg

   When it does burn, it releases relatively little energy.

4. 4

   Its maximum burning velocity is 10 cm/s or less

   Measured at 23°C in dry air. This is what separates 2L from Class 2. ASHRAE uses R-32 as a reference refrigerant at about 6.7 cm/s.

For a sense of scale, ACHR News reported burning velocities of 6.7 cm/s for R-32 and 5.2 cm/s for R-454B². That's slow enough that a flame struggles to sustain itself, which is the practical meaning of "mildly flammable."

Which refrigerants are A2L?

EPA's SNAP listings for residential and light commercial AC and heat pumps show which substitutes are acceptable and at what safety class³. The A2L options all carry use conditions, and all sit at or under the 700 GWP limit for new systems in that sector.

R-454B is a blend of 68.9% R-32 and 31.1% R-1234yf by mass⁴. Which A2L you work on depends on the equipment brand, and they aren't interchangeable.

A2L vs A1 vs A3 refrigerants

Why is the industry switching to A2L refrigerants?

The switch is about global warming potential, not safety. Under the AIM Act's Technology Transitions program, new residential and light commercial AC and heat pump systems must use refrigerants with a GWP of 700 or less⁵. R-410A is far above that line; the A2Ls are under it. See what the AIM Act requires for the bigger picture.

What does A2L change on a service call?

Here's an example. A tech is sent to a two-year-old 3-ton heat pump with a low-charge complaint. The nameplate says R-454B. Compared with the same call on R-410A, a few things change:

The charging math doesn't change: superheat and subcooling still tell you whether the charge is right, using the manufacturer's targets and the PT chart for that refrigerant. Our superheat and subcooling calculator handles the arithmetic.

On new installs, A2L equipment must be certified to UL 60335-2-40, and the 2024 International Residential Code adds checks for refrigerant detection, minimum room size and ignition sources in the ductwork⁷. Which code edition applies depends on what your state or city has adopted.

Do techs need a separate A2L certification?

No federal one. EPA's Section 608 technician certification has applied to appliances containing non-exempt substitute refrigerants since January 1, 2018, and A2Ls are substitutes⁸. Read more in what EPA 608 certification covers. Training still matters: NATE now offers a voluntary Low-GWP refrigerant certification exam, 100 closed-book questions aimed at techs with at least two years of experience⁹, and most manufacturers publish their own A2L procedures.

How TradesWork tracks A2L work

In TradesWork, every charge and recovery is logged on the tech's phone with the refrigerant, ounces, cylinder, job, unit and technician, and cylinders are tracked by barcode with their charge and recovery history. That makes it easy to see which customers have R-454B, R-32 or R-410A equipment before a tech rolls. See warranty and refrigerant tracking.