Safety aspects

Compared to most potential non-fluorocarbon alternatives, the products of the HFC family are in most cases non-flammable and have favourable toxicity profiles, a key factor for consumer applications and for use in public places. It is essential e.g. for installations used in public places like theatres, supermarkets, transportation, tall buildings…

HFCs are often the most reliable and preferred technical solution for a range of applications.
For refrigeration and air-conditioning applications, standards restrict the use or limit the quantity (charge size) for flammable or toxic refrigerants. Where these alternatives can be used additional safety measures required may impose additional costs that could be invested in improved performance including energy consumption.
A new class of fluorocarbons, the HFOs (hydrofluoro-olefins) or as blends with HFCs is enabling the partial replacement of HFCs offering similar safety and performance benefits.

Overall, when selecting a refrigerant, safety issues cannot be overlooked. The major drawbacks of HFC alternatives are the safety characteristics. Ammonia and some hydrocarbons, whilst they are excellent refrigerants, are toxic, and in case of hydrocarbons extremely flammable. They therefore should be used with care, in conditions of safety demanding maximum attention and strict precautions. The Table hereunder illustrates some of the characteristics of different refrigerants from a safety perspective.


The toxicity rating is given in terms of the Occupational Exposure Limit (OEL). The 1000 ppm limit on non-toxic substances is to prevent any danger of suffocation due to oxygen displacement. Flammability properties are characterised by the upper and lower flammability limits (the concentration limits in which the substance is flammable), the energy released during combustion, and by the auto-ignition temperature. More recently to categorise moderately and marginally substances such as some HFCs and the HFOs, flame speed and ignition energy are being utilised.

Compound Refrigerant Number Boiling point (° C) AOEL (ppm) AOSEL (ppm) Cardiotoxicity LOAEL (ppm) Flammability Limits (Vol % in Air) NFPA
AOEL: Acceptable Occupational Long-term exposure Limit (ppm)
AOSEL: Acceptable Occupational Short-term exposure Limit (ppm)
NFPA – National Fire Codes, 2000
LOAEL : Lowest Observed Adverse Effect Level
HFC-32 R-32 -51.8 1000 3000 350,000 14.4-28.9
HFC- 125 R-125 -48.9 1000 3000 100,000 none
HFC-134a R-134a -26.2 1000 3000 80,000 none
HFC-143a R-143a -47.2 1000 3000 300,000 8.2-17.4
HFC-152a R-152a -25 1000 5000 150,000 3.9-16.9
Carbon dioxide R-744 -78.4 5000 30 15,000 none
Propane R-290 -42.1 1000 / / 2.1-9.5
Propylene R-1270 -47.7 / / / 2.4-11
n-Butane R-600 -0.5 800 / / 1.9-8.5
Iso-Butane R-600a -11.7 / / / 1.8-8.4
Ammonia R-717 -33.3 25 35 / 15.5-28
Toxicity and Flammability Characteristics of Certain Refrigerants


See also: Some safety aspects of the different refrigerant types

For more information see the EFCTC Learn about … Alternative refrigerants or HFCs: an obvious choice? Safety first when choosing a refrigerant!

For more information see the EFCTC Learn about … Alternative refrigerants or HFCs: an obvious choice? Safety first when choosing a refrigerant!

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