Natural Refrigerant Fluids

Natural refrigerants are the green alternative to Freon and have a very low environmental impact: their minimal levels of ODP (Ozone Depletion Potential) and GWP (Global Warming Potential) respect the ozone layer, while their contribution to global warming is below the limits laid down by the Kyoto protocol.

Natural refrigerants, being natural gases, fall within the broader scope of SOL’s extensive expertise, as a company specialised in handling gases at high pressure that may also be toxic or inflammable.

Natural refrigerants can be divided into three families:

Ammonia (R717)

Ammonia is a natural refrigerant known for its very high performance in refrigeration cycles. It has been used in the refrigeration industry since the 1930, has a very low boiling point and high energy efficiency thanks mainly to its very high latent heat of evaporation.

In contrast to its excellent refrigerant properties, ammonia is however toxic for man, inflammable and is not compatible with copper circuits. To get around these problems systems with a secondary fluid are used (thus avoiding direct expansion) together with glycol water or carbon dioxide. The complexity of these systems means that ammonia is generally used in large industrial plants, supermarkets or sports facilities.

Carbon dioxide (R744)

Carbon dioxide is the benchmark for the calculation of GWP and is extremely respectful of the environment in terms of global warming, while having no impact on the ozone layer. In the past it was used extensively until the advent of CFCs and HCFCs (which today can no longer be used).

In addition to good heat transmission, carbon dioxide offers high volumetric cooling capacity which makes it possible to use small volume compressors, as well as excellent thermodynamic efficiency at low and medium temperatures. The peculiarity of carbon dioxide compared with other refrigerants is that specially designed plants are necessary to cope with its state diagram (P/T).

It is neither toxic nor inflammable, is not covered by patent, nor are there any limitations on its use worldwide which means that the costs of production and distribution are low compared with other refrigerant gases.


Like ammonia, hydrocarbons were widely employed until the advent of CFCs and HCFCs, both in the home and in industry. Today there is renewed interest in their use, since the absence of both fluorine and chlorine means that they do not damage the environment: almost all domestic fridges currently sold use hydrocarbons.

The use of hydrocarbons for refrigeration has the considerable advantage that, in addition to its excellent heat transporting properties, it means that mineral oils can be used, thus avoiding the problems of humidity linked to the use of synthetic lubricants.

The risks inherent in plants using hydrocarbons are now very low, thanks to the reduced quantity of HC present in the devices, and to the provisions of regulation EN378.


Application table



Commercial refrigeration

Industrial refrigeration 

Heat pumps


Refrigerated transport

R717 Ammonia





R744 Carbon dioxide




R32 Difluoromethane 

R290 Propane

R600 Normal-Butane

R600A Iso-Butane

R-E170A Dimethylether

R170 Ethane


Safety Datasheets

SOL for Industry
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