The future-proof path
Natural refrigerants are substances that also occur in nature and do not have to be produced chemically: carbon dioxide (CO₂), ammonia (NH₃), hydrocarbons such as propane and isobutane, water and air. Their global warming potential is zero or close to zero, and they do not damage the ozone layer (ODP 0). Synthetic, fluorinated refrigerants such as R32, R134a or R410A are not among them.
Natural refrigerants such as CO₂, ammonia and propane are rapidly gaining importance in industrial refrigeration, in refrigeration systems as well as in air conditioning and heat pumps. The reason is their very low or non-existent global warming potential (GWP) – and the European F-gas Regulation, which increasingly restricts climate-damaging synthetic refrigerants (F-gases / HFCs).
Anyone planning or modernising a refrigeration system today is making a an investment-secure and environmentally friendly decision: independent of shrinking HFC quotas, with high efficiency and excellent suitability for heat recovery.
| Property | CO₂ (R744) | Ammonia (R717) | Propane (R290) |
|---|---|---|---|
| Global warming potential (GWP) | 1 | 0 | 0,02 |
| Ozone depletion potential (ODP) | 0 | 0 | 0 |
| Safety class | A1 · non-flammable, non-toxic | B2L · toxic, low flammability | A3 · flammable, non-toxic |
| Pressure level | very high | medium | medium |
| Capacity range | small to large | large | small to medium |
| Strength | Deep freezing, heat recovery | Efficiency at high capacities | Compact chillers |
| Materials | Copper or steel | Steel, no copper | Copper or steel |
GWP = global warming potential (100 years; CO₂ = 1 as reference value) according to Regulation (EU) 2024/573, Annex VI, based on the IPCC Sixth Assessment Report. Older sources give propane a value of 3 from the Fourth Assessment Report. Safety classes according to ASHRAE 34 / DIN EN 378.
the three most important
A1 — non-flammable, non-toxic
Carbon dioxide is the reference refrigerant: its global warming potential (GWP) of 1 defines the scale. It is non-flammable and non-toxic, but operates at high working pressures and with a high volumetric cooling capacity.
Typical Areas of Application
B2L — toxic, mildly flammable
Ammonia has been the most efficient refrigerant in industrial refrigeration for over a hundred years — with a GWP of 0 and no ozone depletion potential. As it is toxic and flammable at higher concentrations, it requires a well-thought-out safety and system concept.
Typical Areas of Application
A3 — flammable, non-toxic
Propane is convincing due to its excellent thermodynamic properties and very high efficiency at a GWP of 0.02. As a flammable refrigerant, it is used safely through charge quantity limitation and a suitable safety concept.
Typical Areas of Application
And water? Water (R718) is also a natural refrigerant, GWP 0, neither flammable nor toxic. Because it freezes at 0 °C and needs very large volume flows in the refrigerant circuit, it is limited to special systems for chilled water above freezing point.
Selection
There is no best natural refrigerant, only the one that suits the system. Three questions almost always decide.
CO₂ is strong for deep freezing, heat recovery and heat pumps with high flow temperatures. For chilled water between about 6 and 12 °C, as data centres and air conditioning require, chillers with propane or ammonia work very efficiently.
For very large cooling capacities in production and logistics, ammonia has been the first choice for decades because of its efficiency. In the small and medium range, propane chillers are gaining ground because they are compact and work with small charges.
Flammable and toxic refrigerants need a suitable location: outdoors, on the roof or in a dedicated machine room. If the system has to stand inside the building, CO₂ is often the simpler solution.
From practice: In the NorthC data centre in Munich, cooling is generated with propane (R290): 1.0 MW of cooling capacity with full redundancy. To the project
Safety
Natural refrigerants have been in use for decades. They are safe when the system and its location suit the substance. Safety requirements are set out in DIN EN 378, depending on toxicity, flammability and pressure. Regular maintenance and leak testing are part of it for all of them.
CO₂ is neither flammable nor toxic, but in large quantities it displaces oxygen. In enclosed rooms, a gas detection system and ventilation are therefore part of the installation. The high operating pressures determine the choice of all components.
Ammonia is toxic, but its pungent smell is noticeable even at very low concentrations, long before it becomes dangerous. The system is installed in a dedicated machine room or outdoors, with gas detection, emergency ventilation and the smallest possible charge.
Propane is flammable. How much of it the system may contain depends on the location and the size of the room. A protection zone is defined around the system in which no ignition sources may be present.
What a safety concept for propane looks like in practice is shown in our article on propane (R290).
The EU F-gas Regulation governs fluorinated greenhouse gases. It gradually reduces the available quantity of partially fluorinated refrigerants (HFCs) and restricts the use of refrigerants with a high GWP in new systems. For operators, this means rising prices and decreasing availability of synthetic refrigerants – with growing legal and planning uncertainty.
Natural refrigerants are not affected by this shortage. They secure system operation in the long term and make investments future-proof – a key argument as early as the planning phase. Which applications already run on natural refrigerants today is shown by the German Environment Agency (Umweltbundesamt).
Frequently asked: R32 is not a natural refrigerant. It is a synthetic, partially fluorinated refrigerant (HFC) and therefore falls under the F-gas Regulation. Its global warming potential is much lower than that of older refrigerants such as R410A, but many times higher than that of CO₂, ammonia or propane. For certain new systems, the regulation is gradually restricting the use of such refrigerants.
At a glance
Very low to zero global warming potential – a direct contribution to CO₂ reduction.
Independent of F-Gas scarcity – long-term availability and investment security.
Excellent thermodynamic properties – low energy consumption and good heat recovery.
A technology proven over decades – reliably in use with the right safety concept.
And the disadvantages? Each natural refrigerant has its own requirements: propane is flammable, ammonia is toxic, CO₂ operates at very high pressures. On top of that, purchase costs for safety technology and components are often higher. With planning, a suitable location and safety technology, these points can be managed.
A system designed for synthetic refrigerants can generally not simply be filled with a natural refrigerant. The refrigerant circuit is designed for different pressures, materials and safety requirements. The switch is made by renewing the cooling generation, often step by step and during ongoing operation.
Modernisation of refrigeration systems · Modernising refrigeration in a data centre
In refrigeration, CO₂ (R744), ammonia (R717) and propane (R290) are the main ones in use. In addition, isobutane (R600a) is used in small appliances such as refrigerators, and water (R718) and air (R729) in special applications.
Natural refrigerants occur in nature, synthetic ones are produced chemically. Most synthetic refrigerants are fluorinated hydrocarbons (PFCs/HFCs), some with a high global warming potential. Older chlorofluorocarbons (CFCs) also damaged the ozone layer and have long been banned.
Yes. The refrigerant R290 is propane, a hydrocarbon that also occurs in natural gas. Its global warming potential is 0.02.
Industrial heat pumps often work with ammonia, CO₂ or propane. Which one suits depends mainly on the required flow temperature and the capacity.
No. R32 is a synthetic, partially fluorinated refrigerant and is subject to the F-gas Regulation.
Ammonia has a global warming potential of 0 and does not deplete ozone.
The system often costs more to purchase because safety technology and components must be matched to the refrigerant. In operation, high efficiency and stable refrigerant prices often make up for this.
KSI Kältetechnik plans, builds and maintains industrial refrigeration systems with natural refrigerants – from the energy concept through plant engineering to 24/7 service.
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