R507A Refrigerant50/50 R125/R143a azeotrope · Legacy low-temperature refrigeration · Flooded-system history
R507A is a 50/50 azeotropic HFC blend of R125 and R143a developed as a zero-ODP replacement for R502 in low- and medium-temperature refrigeration. It is A1 and has essentially zero temperature glide, making it attractive historically for flooded evaporators and commercial refrigeration. Its climate impact is extremely high, however: EPA’s current GWP is 3,985, so R507A has been prohibited in many new and retrofit U.S. refrigeration categories while a legacy service base remains.
What is R507A refrigerant?
R507A is an azeotropic blend that behaves much like a pure refrigerant in phase change. Honeywell historically positioned it for R22/R502 replacement and flooded-system conversions. In 2026 it should be viewed primarily as a legacy high-GWP refrigerant: existing equipment may still require service, but new commercial-refrigeration use is heavily restricted and lower-GWP alternatives dominate current design.
R507A refrigerant properties
Use these values for research and screening. For equipment design, charging and compliance, use the exact supplier PT data, SDS, OEM documentation and regulation that governs the project.
| Property | Reference | Engineering / source note |
|---|---|---|
| Designation | R507A | ASHRAE designation / Genetron AZ-50 |
| Nominal composition | R125/R143a = 50/50 mass % | Honeywell / NIST REFPROP |
| Refrigerant type | Azeotropic HFC blend | Zero/negligible glide |
| Molecular weight | ≈98.9 g/mol | Honeywell |
| Normal boiling point | ≈ −46.7°C | Honeywell product data |
| Critical temperature | ≈70.6°C | Honeywell |
| Critical pressure | ≈37.1 bar | Honeywell |
| ODP | 0 | No ozone depletion |
| 100-year GWP | 3,985 | EPA Technology Transitions |
| Safety classification | A1 | Lower toxicity / no flame propagation |
EPA Technology Transitions uses the values shown on this page. Older product literature may use IPCC AR4/AR5 or another assessment, so a different number is not automatically an error.
Where is R507A used?
Applications must be evaluated by system type, charge, compressor, heat exchanger, safety class and current regulation. The examples below describe recognized use contexts, not automatic approval for every installation.
Legacy supermarket refrigeration
Installed low-temperature racks and cases remain in service.
Flooded evaporator systems
Its azeotropic behavior made R507A historically attractive for flooded conversions.
Ice machines
Legacy commercial ice equipment may contain R507A.
Cold-storage / warehouse refrigeration
Older low-temperature systems used R507A extensively.
Industrial process refrigeration
EPA SNAP still lists R507A as acceptable in some industrial-process contexts, but Technology Transitions rules must also be checked.
Legacy R502 / R22 replacements
R507A historically replaced ozone-depleting refrigerants in selected low-temperature systems.
Continue through the Refrigerant Replacements and Low-GWP Refrigerants hubs for broader selection context.
R507A is genuinely azeotropic: why that mattered
R507A contains equal mass fractions of R125 and R143a and is an azeotropic blend. It has essentially no composition glide during normal evaporation/condensation.
That simplified charging, flooded evaporator operation and control relative to strongly zeotropic retrofit blends.
Honeywell specifically promoted R507A as an azeotropic option for flooded-system conversion, which helps explain its historical niche.
R507A vs R404A: similar era, different composition
R404A contains R125/R143a/R134a at 44/52/4, while R507A eliminates R134a and uses 50/50 R125/R143a.
Both are A1 high-GWP refrigeration blends, but R507A is more strictly azeotropic and EPA’s current GWP is slightly higher: 3,985 versus 3,922 for R404A.
The two should not be mixed or treated as identical even when compressor/application tables list both.
Why U.S. SNAP restrictions on R507A started early
EPA SNAP made R507A unacceptable in retrofit remote-condensing and supermarket applications in 2016 and unacceptable in new supermarket systems beginning January 1, 2017.
Stand-alone equipment restrictions followed by equipment size/temperature class, and refrigerated food processing/dispensing new equipment became unacceptable in 2021.
These SNAP dates predate the AIM Act Technology Transitions program and show that R507A was already being pushed out because of high climate impact.
What to do with an existing R507A system
Existing systems create the same strategic decision as other legacy HFC equipment: repair and maintain, retrofit with an approved lower-GWP refrigerant, or replace the system.
An A1 retrofit blend such as R448A/R449A may simplify the safety-class transition in compatible systems, while new equipment may justify sub-150 A2L or natural-refrigerant architecture.
Recovery, reclamation and refrigerant identification are important because contaminated R404A/R507A recovery cylinders can undermine reclaimed-product quality.
R507A vs R404A
The table highlights engineering differences rather than implying direct interchangeability.
| Characteristic | R507A | R404A |
|---|---|---|
| Composition | R125/R143a = 50/50 | R125/R143a/R134a = 44/52/4 |
| EPA GWP | 3,985 | 3,922 |
| Safety class | A1 | A1 |
| Phase behavior | Azeotropic | Near-azeotropic |
| Glide | Essentially zero | Very small |
| Flooded-system history | Strong | Less distinctive |
| Modern status | Legacy / restricted | Legacy / restricted |
R507A safety: A1 but very high environmental cost of leakage
R507A is A1, so flammability is not the primary hazard. Large releases can displace oxygen, flashing liquid can cause cold injury and hot work can generate decomposition products. With GWP near 4,000, leak prevention, recovery and refrigerant management are particularly important.
High-GWP leakage
A relatively small mass loss has large CO₂-equivalent climate impact.
Cold/pressure hazards
Use appropriate PPE and rated recovery/charging equipment.
Refrigerant identity
Avoid mixing R507A with R404A or retrofit blends in recovery cylinders.
Actual risk depends on charge, release rate, pressure, room volume, ventilation, ignition sources, equipment construction, alarm logic and service condition.
See the Refrigerant Safety Guide for classification context.
R507A refrigerant leak detection
Validate detector response to the finished blend
GasNose includes R507A in its public refrigerant directory. Use compatible infrared, heated-diode / semiconductor or other electronic leak detection depending on the task. Large legacy supermarket/cold-store systems can benefit from fixed monitoring because chronic leakage is both costly and climate-intensive.
Portable service leak detectors, fixed area monitors, A2L mitigation sensors and refrigerant identifiers perform different functions. Define the alarm action and concentration range before selecting the technology.
Regulatory position of R507A in 2026
United States
EPA SNAP lists R507A as unacceptable in retrofit supermarket and remote-condensing equipment from 2016 and in new supermarket systems from 2017, with additional stand-alone and food-processing restrictions later. EPA Technology Transitions now uses GWP 3,985, far above current 700/1,400 and future 150/300 limits used across commercial refrigeration.
European Union
R507A is among the very-high-GWP HFC blends most strongly affected by EU F-gas quota reductions, equipment bans and servicing restrictions. Regulation (EU) 2024/573 further reduces the long-term service and new-equipment space for high-GWP fluorinated gases.
Is R507A being phased out?
R507A is a legacy refrigerant. It still matters because installed equipment exists, but new-system strategy should generally focus on lower-GWP alternatives and architecture rather than extending R507A as a platform.
U.S. refrigeration limits differ by cold storage, supermarket, remote condensing, stand-alone product, industrial process and chiller category. A refrigerant may fit one pathway and fail another.
Use the Refrigerant Regulations Hub for regional research.
What should be compared with R507A?
Compare the real equipment pathway: retrofit vs new system, A1 vs A2L capability, GWP threshold, glide, compressor envelope, energy efficiency and service ecosystem.
Practical misconceptions about R507A
“R507A is the same as R404A.”
They have similar applications but different compositions and exact GWP/phase behavior.
“R507A has glide like R407C.”
R507A is azeotropic and essentially zero-glide.
“A1 means R507A leakage is low impact.”
Its GWP is almost 4,000, making climate impact of leaks very high.
“SNAP acceptance in one industrial category means it is allowed in every new refrigeration system.”
End-use listings and Technology Transitions limits are category-specific.
R507A refrigerant FAQ
Concise answers to common composition, retrofit, glide, safety and regulation questions.
What is R507A?
What is the EPA GWP of R507A?
Is R507A flammable?
Does R507A have temperature glide?
Why was R507A popular in flooded systems?
Is R507A the same as R404A?
Can R507A be used in new U.S. supermarket systems?
Can existing R507A systems still exist?
What are common retrofit options?
How should R507A leaks be monitored?
R507A sources and further reading
This profile uses current EPA regulatory references plus refrigerant supplier, NIST, scientific and GasNose resources. Re-check the latest edition before design or compliance decisions.
Working with R507A or planning a refrigerant transition?
Compare GWP, safety class, temperature glide, equipment compatibility and regulatory lifetime before selecting a refrigerant.
Technical Notice: This page is for refrigerant research and general technical reference. Refrigerant suitability, permitted charge, equipment approval, leak mitigation, servicing procedures and regulatory compliance depend on the exact equipment, installation and jurisdiction. Always verify current manufacturer documentation, SDS, applicable standards and local regulations before selecting, replacing, charging or servicing a refrigerant.