In shortR744 (CO₂) is a non-flammable natural refrigerant with a GWP of 1. With a critical temperature around 31 °C it runs in high-pressure transcritical systems and is increasingly used in supermarket refrigeration and hot water heat pumps.
R744 properties
| Code | R744 |
|---|---|
| Chemical name / composition | Carbon dioxide (CO₂) |
| Family | Natural refrigerant |
| GWP (AR4, 100 years) | 1 |
| ODP | 0 |
| Safety class (ISO 817 / ASHRAE 34) | A1: lower toxicity, non-flammable |
| Boiling point (1 atm) | −78.5 °C (sublimes at 1 atm) |
| Temperature glide | None (pure fluid) |
| Charge equal to 5 t CO₂e | — |
| Status | Next generation |
Where is R744 used?
- Transcritical supermarket booster systems
- Low stage of cascade systems
- Hot water heat pumps
- Cold stores
Service and safety notes
- Non-flammable and low toxicity (A1). A large leak in a closed room can still displace oxygen, so gas detection is recommended in small plant rooms.
- Never charge a system with a refrigerant other than the one on its nameplate; retrofits need manufacturer approval and oil and component checks.
- Charging, recovery and leak checks must be done and recorded by F-gas certified technicians.
R744 and regulations
As a natural refrigerant it is outside F-gas quotas and restrictions. Safety rules for flammability, toxicity and pressure (EN 378 and related standards) still apply to system design, room size and charge.
Alternatives to R744
- R717: Natural refrigerant, GWP 0, B2L
- R290: Hydrocarbon (natural), GWP 3, A3
- R448A: HFO/HFC blend, GWP 1,387, A1
Compare all refrigerants in our refrigerant guide.
Other refrigerants
R12R502R22R123R134aR404AR407CR407FR410AR417AR422DR507AR32R448AR449AR452AR454BR454CR513AR1234yfR1234zeR1233zdR514AR290R600aR1270R717
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Frequently asked questions
What is the GWP of R744?
The 100-year global warming potential (AR4) of R744 is about 1.
Is R744 flammable?
A1: lower toxicity, non-flammable.
What can replace R744?
Depending on the application: R717, R290, R448A. Conversions require manufacturer approval and oil and component checks.