Flammable substances have long been used in household appliances and commercial refrigeration . In addition to ammonia , sulphur dioxide and carbon dioxide , use of non-toxic , but highly flammable , hydrocarbons increased around the end of the 19th century due to their good thermodynamic properties . For example , propane ( R290 ) is suitable for use in commercial refrigeration . It has a boiling point of -42 ° C and can evaporate at temperatures of -40 ° C and higher . Compression with this substance can accommodate large fluctuations in temperature without any issues .

HYDROCARBONS – HIGHLY FLAMMABLE REFRIGERANT WITH EXEMPLARY PERFORMANCE When the first synthetic refrigerant was developed , the aim was to match the good thermodynamic properties of hydrocarbons , while reducing flammability , and thus improve safety and simplify installation . Hydrogen was largely replaced with the halogens chlorine and fluorine and to a lesser degree

with bromine , resulting in the first safety refrigerant . Launched in the 1930s , fully halogenated CFCs soon drove out many of the other substances used in commercial refrigeration and household appliances .

Because chlorine and bromine contribute significantly to the depletion of the ozone layer , today ’ s synthetic refrigerants are primarily fluorinated hydrocarbons . While most of those are partially fluorinated , some are based on monounsaturated hydrocarbons such as propylene , which shortens the atmospheric lifetime and reduces global warming potential . In addition , pure hydrocarbons are still used as refrigerants in a variety of applications such as process cooling in the petrochemicals sector , in commercial refrigeration equipment and in liquid chillers .

AN OVERVIEW OF FLAMMABLE REFRIGERANTS In accordance with the ISO 817 standard , refrigerants are now broken down into Categories A and B . Non-toxic substances belong in Category A , toxic refrigerants in Category B . The degree of flammability is broken down into four groups ( 1 = nonflammable , 2L = flammable with slow spread of flames , 2 = flammable , 3 = highly flammable ).

The most important substances in safety group A3 that offer potential as a refrigerant are hydrocarbons such as propane ( R290 ), propylene ( R1270 ), isobutane ( R600a ), butane ( R600 ) and ethane ( R170 ), which , as explained , have a long history in the refrigeration and air-conditioning industry and served as an example in the development of many synthetic refrigerants .

Group A3 refrigerants are extremely flammable and can ignite at concentrations of two to ten per cent in the air . In a medium concentration , the mere spark of a light switch , a steel tool dropped onto the floor or a statically charged pullover could result in ignition and lead to serious deflagration or explosion . The combustion residues tend to be carbon dioxide and water and are therefore the least dangerous , once everything has had a chance to cool .

The most common refrigerants in the A2L class are hydrofluorocarbons ( HFCs ), hydrofluoroolefins ( HFOs ) and blends of the two . Low fluorination reduces the level of flammability , while offering low or moderate global warming potential . Examples include R1234yf , R32 and R455A . Compared to A3 refrigerants , A2L refrigerants are heavier and capable of ignition at higher concentrations . Flames and serious electrical faults , for example , can provide the necessary ignition energy . In addition to carbon dioxide and water , combustion can also result in high levels of toxic and corrosive residues such as hydrogen fluoride – hydrofluoric acid dissolved in water – and carbonyl fluoride , meaning more intensive precautionary measures need to be taken after combustion .

In a given space , A2L refrigerants can often accommodate much higher charges and therefore higher cooling capacities with the same safety guidelines and without increasing the level of risk . This is advantageous particularly when it comes to compact air conditioning systems and heat pumps . But as long as each refrigeration system is optimally adjusted for the refrigerant in use , there ’ s no discernible

Dr Heinz Jürgensen , director of Application Technology and Special Projects at BITZER .

difference between A2L and A3 refrigerants in terms of system efficiency .

Table : A comparison of some of the physical properties of flammable and nonflammable refrigerants .

A2L REFRIGERANT AND POTENTIAL PFAS BANS IN THE EU The current debate surrounding a potential ban on per- and polyfluoroalkyl substances ( PFASs ) could have an impact on the longterm availability of many A2L refrigerants . According to the definition of the proposed ban , the PFAS substance group covers many HFCs , including HFOs , which due to their low greenhouse effect and low flammability were a preferred solution for fulfilling the requirements of the EU F-Gas Regulation . Authorities in Germany , the Netherlands , Denmark , Sweden and Norway have recommended listing PFASs as substances of concern in EU Regulation 1907 / 2006 ( REACH ) on chemicals , which would make it much more difficult to use PFASs or prohibit them entirely . A sixmonth public consultation on the current recommendation will begin on 22 March 2023 . Potential REACH regulations could take effect in 2025 . It ’ s too soon to accurately predict the results of the debate . However , a potential ban on all alternative refrigerant blends with low GWP would make highly flammable and eco-friendly hydrocarbons in safety group A3 all the more important in the refrigeration and air-conditioning industry in the future .

All photos by BITZER

SCHAUFLER Academy in Rottenburg-Ergenzingen .

SAFETY ASPECTS WHEN USING FLAMMABLE REFRIGERANT Regardless of the flammable refrigerant selected , an expanded risk assessment for work environment needs to be conducted