Refrigerant Safety Classifications
Updated October 19, 2026
ANSI/ASHRAE Standard 34-2022 classifies refrigerants by toxicity (Class A or B) and flammability (Subclass 1, 2L, 2, or 3). The combination — A1, A2L, A3, B1, B2L, and so on — determines equipment requirements, charge limits, refrigerant detection where the standard requires it, and machine room ventilation under codes including UL 60335-2-40 and ASHRAE 15.
Lower toxicity, no flame propagation. The safest category.
Lower toxicity, low burning velocity. Requires A2L-rated equipment + refrigerant detection where the standard requires it.
Lower toxicity, flammable. Uncommon in HVAC.
Lower toxicity, highly flammable. Hydrocarbon class — propane, isobutane, ethylene, propylene.
Higher toxicity, no flame propagation. R-123 and other centrifugal-chiller refrigerants.
Higher toxicity, low burning velocity. Ammonia class — industrial refrigeration.
How to read the class code
Letter (A or B) indicates toxicity. A-class refrigerants have lower toxicity: the Occupational Exposure Limit (OEL) is 400 ppm or higher. B-class refrigerants have higher toxicity, with an OEL below 400 ppm.
| Subclass | Burning velocity | Description |
|---|---|---|
| 1 | No propagation at 60°C in air | Non-flammable per ASTM E681 |
| 2L | ≤ 10 cm/s + LHV < 19,000 kJ/kg | Lower flammability (added to ASHRAE 34 in 2010 for HFCs/HFOs) |
| 2 | 10-100 cm/s | Flammable (uncommon — A2L is usually preferred) |
| 3 | LFL ≤ 0.10 kg/m³ or HoC ≥ 19,000 kJ/kg | Higher flammability (hydrocarbons) |
All refrigerants in the dataset
Click a column heading to sort. Use the filters to narrow by type or class. Each refrigerant name links to its full reference page with PT chart and properties.
| Chemistry | ||||
|---|---|---|---|---|
| R-11 | CFC | A1 Lower toxicity, no flame propagation | CCl3F | 4,750 |
| R-12 | CFC | A1 Lower toxicity, no flame propagation | CCl2F2 | 10,900 |
| R-1224yd(Z) | HCFO | A1 Lower toxicity, no flame propagation | CF3CF=CHCl (Z isomer) | 1 |
| R-1233zd(E) | HCFO | A1 Lower toxicity, no flame propagation | CF3CH=CHCl (E isomer) | 4 |
| R-124 | HCFC | A1 Lower toxicity, no flame propagation | CHClFCF3 | 609 |
| R-125 | HFC (pure) | A1 Lower toxicity, no flame propagation | CHF2CF3 | 3,500 |
| R-13 | CFC | A1 Lower toxicity, no flame propagation | CClF3 | 14,400 |
| R-1336mzz(Z) | HFO (pure) | A1 Lower toxicity, no flame propagation | CF3CH=CHCF3 (Z isomer) | 2 |
| R-134a | HFC (pure) | A1 Lower toxicity, no flame propagation | CH2FCF3 | 1,430 |
| R-218 | PFC | A1 Lower toxicity, no flame propagation | C3F8 | 8,830 |
| R-22 | HCFC | A1 Lower toxicity, no flame propagation | CHClF2 | 1,810 |
| R-236ea | HFC (pure) | A1 Lower toxicity, no flame propagation | CF3CHFCHF2 | 1,370 |
| R-236fa | HFC (pure) | A1 Lower toxicity, no flame propagation | CF3CH2CF3 | 9,810 |
| R-404A | HFC blend | A1 Lower toxicity, no flame propagation | R-143a/R-125/R-134a (52/44/4) | 3,922 |
| R-407A | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-134a (20/40/40) | 2,107 |
| R-407C | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-134a (23/25/52) | 1,774 |
| R-407F | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-134a (30/30/40) | 1,825 |
| R-410A | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125 (50/50) | 2,088 |
| R-417A | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-134a/R-600 (46.6/50.0/3.4) | 2,346 |
| R-421A | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-134a (58/42) | 2,631 |
| R-422A | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-134a/R-600a (85.1/11.5/3.4) | 3,143 |
| R-422B | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-134a/R-600a (55/42/3) | 2,526 |
| R-422D | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-134a/R-600a (65.1/31.5/3.4) | 2,729 |
| R-427A | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-143a/R-134a (15/25/10/50) | 2,138 |
| R-438A | HFC blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-134a/R-600/R-601a (8.5/45/44.2/1.7/0.6) | 2,265 |
| R-448A | HFC/HFO blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-1234yf/R-134a/R-1234ze(E) (26/26/20/21/7) | 1,386 |
| R-449A | HFC/HFO blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-1234yf/R-134a (24.3/24.7/25.3/25.7) | 1,396 |
| R-450A | HFC/HFO blend | A1 Lower toxicity, no flame propagation | R-134a/R-1234ze(E) (42/58) | 601 |
| R-452A | HFC/HFO blend | A1 Lower toxicity, no flame propagation | R-32/R-125/R-1234yf (11/59/30) | 2,140 |
| R-500 | CFC blend (azeotrope) | A1 Lower toxicity, no flame propagation | R-12/R-152a (73.8/26.2) | 8,077 |
| R-502 | CFC blend (azeotrope) | A1 Lower toxicity, no flame propagation | R-22/R-115 (48.8/51.2) | 4,657 |
| R-503 | CFC blend (azeotrope) | A1 Lower toxicity, no flame propagation | R-23/R-13 (40.1/59.9) | 14,560 |
| R-507A | HFC blend | A1 Lower toxicity, no flame propagation | R-125/R-143a (50/50) | 3,985 |
| R-513A | HFC/HFO blend | A1 Lower toxicity, no flame propagation | R-134a/R-1234yf (44/56) | 630 |
| R-515A | HFO blend | A1 Lower toxicity, no flame propagation | R-1234ze(E)/R-227ea (88/12) | 387 |
| R-515B | HFO blend | A1 Lower toxicity, no flame propagation | R-1234ze(E)/R-227ea (91.1/8.9) | 287 |
| R-744 | Natural | A1 Lower toxicity, no flame propagation | CO2 | 1 |
| R-C318 | PFC | A1 Lower toxicity, no flame propagation | c-C4F8 | 10,300 |
| R-1234yf | HFO (pure) | A2L Lower toxicity, lower flammability | CF3CF=CH2 | 1 |
| R-1234ze | HFO (pure) | A2L Lower toxicity, lower flammability | CHF=CHCF3 | 1 |
| R-1234ze(E) | HFO (pure) | A2L Lower toxicity, lower flammability | CHF=CHCF3 (E isomer) | 1 |
| R-1234ze(Z) | HFO (pure) | A2L Lower toxicity, lower flammability | CHF=CHCF3 (Z isomer) | <1 |
| R-143a | HFC (pure) | A2L Lower toxicity, lower flammability | CH3CF3 | 4,470 |
| R-32 | HFC (pure) | A2L Lower toxicity, lower flammability | CH2F2 | 675 |
| R-452B | HFC/HFO blend | A2L Lower toxicity, lower flammability | R-32/R-1234yf/R-125 (67/26/7) | 698 |
| R-454B | HFC/HFO blend | A2L Lower toxicity, lower flammability | R-32/R-1234yf (68.9/31.1) | 465 |
| R-454C | HFC/HFO blend | A2L Lower toxicity, lower flammability | R-32/R-1234yf (21.5/78.5) | 146 |
| R-455A | HFC/HFO blend | A2L Lower toxicity, lower flammability | CO2/R-32/R-1234yf (3/21.5/75.5) | 146 |
| R-457A | HFC/HFO blend | A2L Lower toxicity, lower flammability | R-32/R-152a/R-1234yf (18/12/70) | 137 |
| R-516A | HFC/HFO blend | A2L Lower toxicity, lower flammability | R-1234yf/R-134a/R-152a (77.5/8.5/14) | 140 |
| R-152a | HFC (pure) | A2 Lower toxicity, flammable | CH3CHF2 | 124 |
| R-365mfc | HFC (pure) | A2 Lower toxicity, flammable | CF3CH2CF2CH3 | 794 |
| R-1150 | Hydrocarbon | A3 Lower toxicity, higher flammability | C2H4 | 3.7 |
| R-1270 | Hydrocarbon | A3 Lower toxicity, higher flammability | C3H6 | 1.8 |
| R-290 | Hydrocarbon | A3 Lower toxicity, higher flammability | C3H8 | 3.3 |
| R-600a | Hydrocarbon | A3 Lower toxicity, higher flammability | C4H10 (isomer) | 1 |
| R-123 | HCFC | B1 Higher toxicity, no flame propagation | CHCl2CF3 | 77 |
| R-245fa | HFC (pure) | B1 Higher toxicity, no flame propagation | CHF2CH2CF3 | 1,030 |
| R-514A | HFO blend | B1 Higher toxicity, no flame propagation | R-1336mzz(Z)/R-1130(E) (74.7/25.3) | 3 |
| R-717 | Natural | B2L Higher toxicity, lower flammability | NH3 | 1 |
A2L deep dive — the residential AC transition class
A2L is the most consequential safety class for the 2024-2026 HVAC transition. R-32 and R-454B (both A2L) are replacing R-410A (A1) as the dominant residential AC refrigerants under the AIM Act. The lower flammability nature of A2L refrigerants requires equipment design and installation accommodations that A1 systems don't need.
- A2L-listed equipment or ignition-source isolation in any enclosure with potential refrigerant accumulation.
- Leak detection (refrigerant sensor + alarm) on larger systems above a charge threshold.
- Charge limit calculation from the lower flammability limit (LFL), room floor area, and installation height.
- Mechanical ventilation requirements in some occupancy categories above threshold charge.
- Labeling and installer training.
The maximum permitted charge is not a fixed number per refrigerant. It depends on the refrigerant's lower flammability limit (LFL) and the size of the room the equipment serves. A refrigerant with a lower LFL permits less charge in a given room, and a larger room permits more charge.
These charge limits drive equipment design for A2L: residential split systems above the threshold need either multiple smaller indoor units (distributing charge) or single-zone systems sized to stay below the limit per room. For installations in tight spaces (closets, small mechanical rooms), additional safety devices may be required.
Sector-by-class compatibility guide
Each safety class fits specific application sectors based on equipment design feasibility, charge size, occupancy, and regulatory acceptance.
| Class | Typical applications | Key requirement |
|---|---|---|
| A1 | Residential AC (R-22, R-410A), commercial refrigeration (R-404A, R-448A, R-449A), mobile AC (R-134a), chillers (R-134a, R-513A, R-1233zd) | Standard ASHRAE 15 — no special equipment |
| A2L | Residential AC (R-32, R-454B), commercial refrigeration (R-454C, R-455A), mobile AC (R-1234yf) | A2L-rated equipment, charge limits, refrigerant detection where the standard requires it (IEC 60335-2-40 for AC and heat pumps; 60335-2-89 for commercial refrigeration) |
| A2 | Uncommon in HVAC. R-152a (limited mobile AC use) | Higher burning velocity than A2L; A2L preferred |
| A3 | Hydrocarbons — R-290 (propane), R-600a (isobutane), R-1270 (propylene). Hermetic chest freezers, domestic refrigerators | Small-charge only per IEC 60335-2-24; spark-controlled service |
| B1 | R-123 (centrifugal chillers in dedicated mechanical rooms) | Machine-room monitoring per ASHRAE 15; R-123 production ends 2030 |
| B2L | R-717 (ammonia) industrial refrigeration — food processing, cold storage, ice rinks | IIAR 2/9 installation, machine room, full-face SCBA for service |
| B3 | Rare. R-1140 historical, specialty industrial only | Not used in modern HVAC |
Service-side implications by class
Beyond equipment design, the safety class affects how a technician handles the refrigerant in the field.
| Class | Service-side requirements |
|---|---|
| A1 | Standard EPA Section 608 procedures. Recovery, recycling, reclaiming per 40 CFR Part 82. Standard electronic leak detectors. |
| A2L | EPA Section 608 procedures. A2L-rated recovery cylinders. No ignition sources during service (no torch-brazing near open refrigerant, no electrical sparks). Refrigerant-specific leak detectors. |
| A3 | Hydrocarbon-specific training. Spark-resistant tools or all-tools-removed during service. Ventilated spaces only. Small-charge limit (hermetic). |
| B-class | Class-specific certification (IIAR for ammonia). PPE includes full-face SCBA for ammonia, vapor-resistant suit for fluorinated B. Machine-room procedures and emergency response plans required. |
Historical evolution — how we got here
HVAC refrigerant safety classifications have evolved alongside the chemistry transitions of the last century.
| Era | Refrigerants | Driver |
|---|---|---|
| 1930s-1970s | CFCs (R-12, R-11, R-502) — A1 class | Safe to handle, but ozone-depleting (discovered 1970s) |
| 1987-2010s | HCFCs (R-22, R-123) — A1/B1 | Montreal Protocol forced CFC phase-out; HCFCs are interim lower-ODP option |
| 2000s-2020s | HFCs (R-410A, R-134a, R-404A) — A1 | HCFC phase-out (R-22 ends 2020); HFCs are zero-ODP but high-GWP |
| 2020s-2030s | A2L (R-32, R-454B, R-454C) + naturals (R-744, R-290, R-717) | AIM Act + EU F-Gas climate phase-down. First mainstream shift away from A1 |
The 2020s-2030s shift is structurally different from prior transitions: this is the first time HVAC residential equipment design has shifted from A1 to A2L in mainstream applications, requiring industry-wide equipment re-certification, installation procedure updates, and service training.
How ASHRAE Standard 34 classification is actually determined
ASHRAE 34 classification is determined by laboratory testing per standardized protocols, not by manufacturer self-declaration. Toxicity (A vs B) comes from Occupational Exposure Limit testing: Class A = time-weighted OEL ≥ 400 ppm, Class B = OEL < 400 ppm. The OEL typically matches the AIHA Workplace Environmental Exposure Limit (WEEL) for the substance.
| Subclass | Test outcome |
|---|---|
| 1 | No flame propagation at 60°C / 101.3 kPa in humid air per ASTM E681 |
| 2L | Flame propagates, burning velocity ≤ 10 cm/s, LHV < 19,000 kJ/kg, LFL > 0.10 kg/m³. "L" suffix added to ASHRAE 34 in 2010 to accommodate R-32 / R-1234yf |
| 2 | Burning velocity 10-100 cm/s. Uncommon — A2L is preferred for similar applications |
| 3 | ASHRAE 34 class 3: LFL ≤ 0.10 kg/m³ OR heat of combustion ≥ 19,000 kJ/kg. Hydrocarbons (R-290, R-600a, R-1270) |
Why A2L matters so much for the 2024-2026 transition
The AIM Act phase-down forces residential AC away from R-410A (A1, GWP 2,088). The only sub-700 GWP refrigerants that satisfy residential AC's pressure envelope and equipment design constraints are A2L: R-32 (GWP 675, A2L) and R-454B (GWP 465, A2L).
Charge limits — the practical A2L constraint
UL / IEC 60335-2-40 specifies a maximum refrigerant charge per room based on the refrigerant's lower flammability limit (LFL), the room floor area, and the installation height.
For typical residential rooms, the calculated limit is generally sufficient for 2-3 ton residential AC using R-32 or R-454B. Larger systems (5+ ton, large multi-zone) split charge across multiple indoor units or use central-ducted systems where refrigerant charge concentrates in outdoor / attic-mounted air handlers with only liquid line at the indoor coil.
Commercial refrigeration with A2L (R-454C, R-455A) follows IEC 60335-2-89 with its own charge limit framework. Limits are higher because equipment typically sits in dedicated rooms or large commercial spaces.
B-class refrigerants and machine room requirements
Class B refrigerants (R-123, R-717 ammonia) are higher-toxicity and require purpose-built installations.
| Refrigerant | Class | Standard | Use |
|---|---|---|---|
| R-123 | B1 | ASHRAE 15 machine-room monitoring | Centrifugal chillers (production ends 2030) |
| R-717 | B2L | IIAR 2 (install) + IIAR 9 (min. safety) | Industrial refrigeration — food processing, cold storage, ice rinks |
Both require purpose-built equipment rooms with refrigerant-specific detection, emergency response procedures, technician PPE (SCBA for ammonia), and machine-room ventilation rated for the specific refrigerant. This is industrial-refrigeration territory, not residential or light commercial HVAC.
How to verify a refrigerant's safety class
Three authoritative sources for safety classification:
| Source | Coverage | Access |
|---|---|---|
| ANSI/ASHRAE Standard 34 | Complete list, updated every 3-4 yrs (current: 2022). Composition, classifications, physical properties. | Purchase from ASHRAE (~$130) |
| Manufacturer SDS | Required by OSHA HazCom (29 CFR 1910.1200). Classification + toxicity + flammability + first-aid + handling. | Free from manufacturer |
| EPA SNAP listing | SNAP (40 CFR Part 82 Subpart G) — refrigerants approved by end-use sector with use conditions. | Free at epa.gov/snap |
For ground-truth verification on an unfamiliar refrigerant, the manufacturer SDS is the most accessible. Every refrigerant cylinder arrives with an SDS in shipment paperwork, and the manufacturer's website hosts the current SDS for download. Cross-check with EPA SNAP for approved applications.
Why classifications matter for everyday work
Beyond the obvious safety implications, the ASHRAE 34 classification drives several practical decisions:
| Decision area | Class-driven impact |
|---|---|
| Service equipment selection | A2L = spark-resistant tools + A2L-rated detection. A3 = stricter ignition-source controls. B-class = class-specific PPE + machine room. |
| Installation location & sizing | A2L charge limits (IEC 60335-2-40) affect closet vs distributed-indoor-unit decision. B-class mandates dedicated equipment rooms. |
| Technician certification | EPA Section 608 has class endorsements; some jurisdictions require additional A2L / A3 training beyond base 608. |
| Building code compliance | ASHRAE 15 sets occupancy-based refrigerant quantity limits by safety class. Some commercial occupancies (assembly, healthcare, detention) have stricter limits. |
| Insurance & warranty | Building insurance + equipment warranty often reference compliance with ASHRAE 15 + UL 60335-2-40 (A2L) + IIAR 2/9 (ammonia). Improper installation voids coverage. |