HyChill Australia general manager, Mario Balen, explains why the term mild flammability is about as logical as a mild pregnancy.

The introduction of "mild" flammability by the F-gas industry is similar to the introduction of "mild" cigarettes by the tobacco industry.

Yes it's true the term mild flammability does exist, although it is hard to believe anyone could come up with such a misnomer, but if you want to check for yourself it is in the ASHRAE refrigerants classification under the AS 5149 refrigerant standards.

So what is flammability? One of the most widely accepted definitions puts it as the ability of a substance to burn or ignite, causing fire or combustion.

Since the material cannot be destroyed, just changed, combustion involves a chemical reaction, typically between the burning material and oxygen. Examples of flammable substances include petrol, ethanol, rubber, alcohol, paper, natural gas and even wood. So what then is "mild" flammability?

That is trickier to explain. For starters, famous physicists and chemists like Newton, Lavoisier, Boyle or even Nobel never worked for DuPont or Honeywell and thus never came even close to such a concept. Somewhat naively, they thought that if it burns, it must be flammable, or at least combustible.

This is where modern science shone through: not only that some refrigerants have a higher flammability, others can have either lower or even mild flammability. Why grades such as moderate, very low, extremely low and ultra-low flammability were omitted is not entirely clear. What is clear is that, when compared with hydrocarbons, those with "mild" flammability burn slower, create less heat of combustion and need higher concentration in air to burn.

I am sure you notice the key words here which are "compared to hydrocarbons". For that is the main and only reason for this classification to be invented and introduced into otherwise serious engineering and scientific disciplines of refrigeration and chemistry. Synthetic refrigerant manufacturers spent 30 years warning about the dangers of hydrocarbon flammability, so there was a slight problem when their latest products, namely R32 and R1234yf, were flammable!

Their solution? Create the Mild Flammability myth. This concept of mild, useful and good has not yet caught up with other avenues of life and technology. In the same vein, medicine is yet to recognise mild pregnancy cases.

Plumbers and welders deal with various flammable gases – they would surely know a thing or two about "mild" flammability. It does not appear so – they too classify them only as flammable or not. It seems that the HVACR industry is on its own in this regard. The Dangerous Goods Code didn’t get it either as both the Australian and the international code classifies substances only as flammable or non-flammable.

Consequently, WorkSafe authorities of various Australian states recognise all flammable refrigerants only as Class 2.1 (flammable). I didn't dare ask fire authorities about their view on mild flammability.

Even those who were instrumental in propagating the "mild" flammability myth started developing doubts. ASHRAE, for example, suddenly decided to put on a myth-busters cap and investigate the real-life flammability of "mildly" flammable A2L refrigerants, although they only looked into "typical" applications, for some reason neglecting to investigate higher charge levels. The results were published in June 2017 in their final report, which states:

"The low burning velocity of 2L refrigerants does not prevent rapid flame spread under many conditions observed", and
"For some classes of refrigeration equipment (…) medium or large leaks can cause refrigerant accumulation in the cold storage compartment.

Since these 2L refrigerants are heavier than air, flammable concentrations can be reached fairly easily in such confined spaces. When a door is opened, there is a spill of refrigerant to a floor level leading to possible ignition..." and "… more investigation is needed." So, what have we learned?

"Mildly" flammable refrigerants burn. Even though "mildly" flammable refrigerants have lower burning velocity, they burn fast. Burning causes fire. Fire is hazardous.

Looks like the Mild Flammability Myth has gone up in flames!


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