Refrigerant Reference
A2L Refrigerant Properties
GWP, ASHRAE safety class, and LFL for the refrigerants of the A2L transition, and what replaces what as new AC and heat pump equipment moves off R-410A.
Refrigerant Properties Comparison
| Refrigerant | GWP | Safety class | LFL (kg/m³) | Role in the transition |
|---|---|---|---|---|
| R-454B | 465 | A2L | 0.35 | Primary R-410A replacement in new ducted systems (Carrier Puron Advance, Trane, York) |
| R-32 | 675 | A2L | 0.31 | R-410A replacement in most mini-splits and Daikin/Goodman unitary equipment |
| R-452B | 698 | A2L | 0.31 | R-410A replacement in some ducted equipment |
| R-410A | 2,088 | A1 | None (A1) | Outgoing nonflammable HFC standard for AC and heat pumps (2010-2025) |
| R-22 | 1,810 | A1 | None (A1) | Legacy HCFC, production ended 2020, reclaimed supply only |
| R-407C | 1,774 | A1 | None (A1) | Legacy A1 R-22 replacement blend |
| R-134a | 1,430 | A1 | None (A1) | Medium-temp refrigeration, chillers, automotive AC |
| R-404A | 3,922 | A1 | None (A1) | Commercial refrigeration, high GWP, being phased down |
| R-454A | 237 | A2L | 0.29 | Lower-GWP blend for refrigeration and some AC |
| R-454C | 146 | A2L | 0.29 | Low-GWP blend for refrigeration |
| R-1234yf | 1 | A2L | 0.29 | Pure HFO, automotive AC and chillers |
| R-290 | 3 | A3 | 0.038 | Propane, higher flammability, small-charge self-contained equipment |
Notes: R-454B GWP is 465 per EPA's table; manufacturer sheets often cite 466 (the difference is immaterial). R-22 GWP is 1,810 on the AR4 basis EPA and ASHRAE historically use; EPA's ozone page lists 1,760 on the newer AR5 basis. A1 refrigerants are nonflammable and have no LFL rating.
ASHRAE Safety Classes
ASHRAE Standard 34 rates refrigerants by toxicity (A lower, B higher) and flammability (1 none, 2L lower, 2 higher, 3 highest). The classes that matter for the current transition:
- A1 (R-410A, R-22, R-134a, R-407C, R-404A): lower toxicity, no flame propagation. Nonflammable.
- A2L (R-454B, R-32, R-452B, R-1234yf): lower toxicity, mildly flammable with a burning velocity at or below 10 cm/s. Requires leak detection and reduced charge limits.
- A3 (R-290 propane, R-600a isobutane): lower toxicity, highly flammable. Restricted to small charges in self-contained equipment.
The A2L class is the whole point of the transition: it keeps flammability low enough to use in ducted and split systems (with the right safety controls) while cutting GWP by 70% or more versus R-410A.
Frequently Asked Questions
What is the GWP of R-454B?
R-454B has a GWP of 465 per EPA's Technology Transitions reference table (many manufacturer datasheets cite 466). That is roughly 78% lower than R-410A's GWP of 2,088, which is why R-454B is the designated replacement.
Is R-32 flammable?
R-32 is classified A2L (mildly flammable) by ASHRAE Standard 34. It ignites only at high concentrations with a strong ignition source and burns slowly, with a maximum burning velocity at or below 10 cm/s. It is far less flammable than A3 refrigerants like propane.
What is replacing R-410A?
R-454B and R-32 are the primary A2L replacements for R-410A in new residential and light-commercial air conditioners and heat pumps, for equipment manufactured from January 1, 2025 under the EPA Technology Transitions rule. R-454B leads in ducted systems, R-32 in mini-splits.
What does A2L mean?
A2L is an ASHRAE Standard 34 safety classification. The A means lower toxicity, and 2L means lower flammability: a heat of combustion under 19,000 kJ/kg and a maximum burning velocity at or below 10 cm/s. A2L sits between nonflammable A1 and the more flammable A2 and A3 classes.
What is the GWP of R-410A?
R-410A has a GWP of 2,088 on the AR4 basis EPA uses (the 40 CFR 84.64(b) computation gives 2,087.5). It is a nonflammable A1 blend of R-32 and R-125, and its high GWP is the reason for the transition to A2L refrigerants.
Is R-454B a drop-in replacement for R-410A?
No. R-454B requires equipment designed and listed for A2L refrigerants, with leak detection, reduced charge limits, and revised components per UL 60335-2-40 and ASHRAE 15.2. It is not a drop-in for existing R-410A systems, which continue to be serviced with R-410A.
Related Calculators & Charts
A2L Charge Limit Calculator
Maximum R-454B or R-32 charge for a room, or minimum room area for a charge, per UL 60335-2-40 and ASHRAE 15.2.
Superheat & Subcooling Calculator
Check charge on R-454B, R-32, R-410A, and 7 more refrigerants with PT interpolation and the four-quadrant diagnostic.
EPA Refrigerant Leak Rate Calculator
Topping off a 15+ lb system triggers a leak rate calculation under 40 CFR 84.106 as of January 1, 2026.
Know the refrigerant. Check the charge and the room limit.
A2L refrigerants come with charge limits tied to room size. The charge limit calculator runs the UL 60335-2-40 and ASHRAE 15.2 math for R-454B, R-32, and more.