Refrigerant Safety Classifications
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, leak detection, 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 + leak detection.
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 | Mildly flammable (added to ASHRAE 34 in 2010 for HFCs/HFOs) |
| 2 | 10-100 cm/s | Flammable (uncommon — A2L is usually preferred) |
| 3 | > 100 cm/s or LHV > 19,000 kJ/kg | Highly flammable (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 | A1Non-flammable | CCl3F | 4,750 |
| R-12 | cfc | A1Non-flammable | CCl2F2 | 10,900 |
| R-1224yd(Z) | hfo pure | A1Non-flammable | CF3CF=CHCl (Z isomer) | 1 |
| R-1233zd(E) | hfo pure | A1Non-flammable | CF3CH=CHCl (E isomer) | 1 |
| R-1233zd(Z) | hfo pure | A1Non-flammable | CF3CH=CHCl (Z isomer) | — |
| R-124 | hcfc | A1Non-flammable | CHClFCF3 | 527 |
| R-125 | hfc pure | A1Non-flammable | CHF2CF3 | 3,500 |
| R-13 | cfc | A1Non-flammable | CClF3 | 14,400 |
| R-1336mzz(Z) | hfo pure | A1Non-flammable | CF3CH=CHCF3 (Z isomer) | 2 |
| R-134a | hfc pure | A1Non-flammable | CH2FCF3 | 1,430 |
| R-218 | hfc pure | A1Non-flammable | C3F8 | 8,830 |
| R-22 | hcfc | A1Non-flammable | CHClF2 | 1,810 |
| R-236ea | hfc pure | A1Non-flammable | CF3CHFCHF2 | 1,370 |
| R-236fa | hfc pure | A1Non-flammable | CF3CH2CF3 | 9,810 |
| R-404A | hfc blend | A1Non-flammable | R-143a/R-125/R-134a (52/44/4) | 3,922 |
| R-407A | hfc blend | A1Non-flammable | R-32/R-125/R-134a (20/40/40) | 2,107 |
| R-407C | hfc blend | A1Non-flammable | R-32/R-125/R-134a (23/25/52) | 1,774 |
| R-407F | hfc blend | A1Non-flammable | R-32/R-125/R-134a (30/30/40) | 1,825 |
| R-410A | hfc blend | A1Non-flammable | R-32/R-125 (50/50) | 2,088 |
| R-417A | hfc blend | A1Non-flammable | R-125/R-134a/R-600 (46.6/50.0/3.4) | 2,346 |
| R-421A | hfc blend | A1Non-flammable | R-125/R-134a (58/42) | 2,630 |
| R-422A | hfc blend | A1Non-flammable | R-125/R-134a/R-600a (85.1/11.5/3.4) | 3,143 |
| R-422B | hfc blend | A1Non-flammable | R-125/R-134a/R-600a (55/42/3) | 2,526 |
| R-422D | hfc blend | A1Non-flammable | R-125/R-134a/R-600a (65.1/31.5/3.4) | 2,729 |
| R-427A | hfc blend | A1Non-flammable | R-32/R-125/R-143a/R-134a (15/25/10/50) | 2,138 |
| R-438A | hfc blend | A1Non-flammable | R-32/R-125/R-134a/R-600/R-601a (8.5/45/44.2/1.7/0.6) | 2,265 |
| R-448A | hfc blend | A1Non-flammable | R-32/R-125/R-1234yf/R-134a/R-1234ze (26/26/20/21/7) | 1,387 |
| R-449A | hfc blend | A1Non-flammable | R-32/R-125/R-1234yf/R-134a (24.3/24.7/25.3/25.7) | 1,397 |
| R-450A | hfc blend | A1Non-flammable | R-134a/R-1234ze(E) (42/58) | 605 |
| R-452A | hfc blend | A1Non-flammable | R-32/R-125/R-1234yf (11/59/30) | 2,140 |
| R-500 | cfc | A1Non-flammable | R-12/R-152a (73.8/26.2) | 8,077 |
| R-502 | hcfc | A1Non-flammable | R-22/R-115 (48.8/51.2) | 4,657 |
| R-503 | cfc | A1Non-flammable | R-23/R-13 (40.1/59.9) | 13,600 |
| R-507A | hfc blend | A1Non-flammable | R-125/R-143a (50/50) | 3,985 |
| R-513A | hfc blend | A1Non-flammable | R-134a/R-1234yf (44/56) | 631 |
| R-515A | hfo blend | A1Non-flammable | R-1234ze(E)/R-227ea (88/12) | 392 |
| R-515B | hfo blend | A1Non-flammable | R-1234ze(E)/R-227ea (91.1/8.9) | 293 |
| R-744 | natural | A1Non-flammable | CO2 | 1 |
| R-c318 | hfc pure | A1Non-flammable | c-C4F8 | 10,300 |
| R-1234yf | hfo pure | A2LMildly flammable | CF3CF=CH2 | — |
| R-1234ze | hfo pure | A2LMildly flammable | CHF=CHCF3 | — |
| R-1234ze(E) | hfo pure | A2LMildly flammable | CHF=CHCF3 (E isomer) | — |
| R-1234ze(Z) | hfo pure | A2LMildly flammable | CHF=CHCF3 (Z isomer) | — |
| R-143a | hfc pure | A2LMildly flammable | CH3CF3 | 4,470 |
| R-32 | hfc pure | A2LMildly flammable | CH2F2 | 675 |
| R-452B | hfo blend | A2LMildly flammable | R-32/R-1234yf/R-125 (67/26/7) | 698 |
| R-454B | hfo blend | A2LMildly flammable | R-32/R-1234yf (68.9/31.1) | 466 |
| R-454C | hfo blend | A2LMildly flammable | R-32/R-1234yf (21.5/78.5) | 148 |
| R-455A | hfo blend | A2LMildly flammable | CO2/R-32/R-1234yf (3/21.5/75.5) | 148 |
| R-457A | hfo blend | A2LMildly flammable | R-32/R-152a/R-1234yf (18/12/70) | 139 |
| R-516A | hfo blend | A2LMildly flammable | R-1234yf/R-134a/R-152a (77.5/8.5/14) | 142 |
| R-152a | hfc pure | A2Flammable | CH3CHF2 | 124 |
| R-365mfc | hfc pure | A2Flammable | CF3CH2CF2CH3 | 794 |
| R-1150 | hc | A3Highly flammable | C2H4 | 4 |
| R-1270 | hc | A3Highly flammable | C3H6 | 2 |
| R-290 | hc | A3Highly flammable | C3H8 | 3 |
| R-600a | hc | A3Highly flammable | C4H10 (isomer) | 3 |
| R-123 | hcfc | B1Toxic, non-flammable | CHCl2CF3 | 77 |
| R-245fa | hfc pure | B1Toxic, non-flammable | CHF2CH2CF3 | 1,030 |
| R-514A | hfo blend | B1Toxic, non-flammable | R-1336mzz(Z)/R-1130(E) (74.7/25.3) | 2 |
| R-717 | natural | B2LToxic + mildly flammable | NH3 | 0 |
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 mildly flammable nature of A2L refrigerants requires equipment design and installation accommodations that A1 systems don't need.
- Sealed motor enclosures 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 per room floor area: m_max = LFL × 4 × A^0.5 × h_0 (LFL = lower flammability limit, A = room area, h_0 = installation height).
- Mechanical ventilation requirements in some occupancy categories above threshold charge.
- Labeling and installer training (EPA Section 608 expanded for A2L handling in 2025).
| Refrigerant | m_max (kg) | m_max (lb) | Note |
|---|---|---|---|
| R-32 | 1.84 | 4.05 | 2-3 ton residential AC |
| R-454B | 2.18 | 4.81 | Slightly higher than R-32 |
| R-1234yf | 1.10 | 2.42 | Most stringent |
| R-1234ze | 1.50 | 3.31 | Mid-range |
Values for a typical 25 m² room at 2.2 m installation height. Different room geometries produce different limits per the formula.
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, leak detection (IEC 60335-2-40) |
| 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 60335-2-89; 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 + A2L-specific training (added 2025). 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 (~150 g 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 | Burning velocity > 100 cm/s OR LHV > 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 2088). 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 466, A2L). There's no A1 path forward at sub-700 GWP — the chemistry of low-GWP refrigerants intrinsically includes mild flammability.
Charge limits — the practical A2L constraint
UL / IEC 60335-2-40 specifies maximum refrigerant charge per room volume based on refrigerant flammability characteristics. The formula: m_max = LFL × 4 × A^0.5 × h_0 where LFL is the lower flammability limit (kg/m³), A is room floor area (m²), and h_0 is installation height (m).
For typical residential rooms (25 m² at 2.2 m height): about 1.8 kg (4 lb) for R-32 and 2.2 kg (4.8 lb) for R-454B — sufficient for 2-3 ton residential AC. 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 — higher limits 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 a cascade of 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. |