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Kilowatt Heating, Air Conditioning and Electrical Blog

A Short History of Air Conditioning Refrigerant


Refrigerant is a critical part of air conditioning systems and of most refrigeration equipment, such as refrigerators and freezers. Although people associate the word refrigerant with cold, refrigerant actually goes through stages of low and high temperatures. What refrigerant does is allow for the process of heat exchange: refrigerant can easily shift between liquid and gaseous states, and as it does this it absorbs and releases heat. In an AC, the refrigerant absorbs heat from the indoor air and then expels it to the outdoor air.

There isn’t a single refrigerant type: many different chemicals have done this job. Usually, these refrigerants are referred to as blends. The word freon is also used to describe refrigerants, but this isn’t accurate, as we’ll talk about below when we look into refrigerant history.

The Early Explosive and Toxic Days

The first electro-mechanical air conditioning system was invented in 1902. It was designed to control humidity inside a Chicago paper plant. This and other early air conditioning systems used a range of chemicals for refrigerant: ammonia, sulfur dioxide, carbon dioxide, and methyl chloride. There was a problem with these chemicals, however: they were either highly toxic, highly flammable, or both. Because of this, air conditioning systems were only used for commercial and industrial purposes. It wasn’t until the 1920s that the first central ACs entered homes, but they were prohibitively expensive and found in only a few wealthy mansions.

The Dawn of Freon

The chemical company DuPont found a way to create a safer form of refrigerant in 1931 when it introduced Freon 12. Freon has remained a trademark of DuPont, so the word freon only refers to a certain type of refrigerant, although in casual use it can refer to any refrigerant. The new line of safer refrigerants used fluorocarbons, both chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). The most common blends used in refrigeration equipment were CFC-12 and HCFC-22, a.k.a. monochlorodifluoromethane, which was the main refrigerant found in air conditioners for decades.

The Standardization

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) started to standardize the naming convention of refrigerants, with all refrigerant blends beginning with the letter “R” followed by a number representing the molecular structure. HCFC-22 became R-22, although still mostly referred to as “freon.” Other blends included R-12 and R-134A. 

The R-22 Phase-Out and the Dawn of R-410A

R-22 was the residential AC standard for several decades. However, HCFCs posed a danger to the ozone layer, and in the 1990s a program was started to gradually phase out R-22 from use. Its replacement is R-410A, invented in 1996, which is a mixture of difluoromethane and pentafluoroethane that doesn’t harm the ozone layer. It often goes under the DuPont-trademarked name Puron

As of 2020, R-22 has been completely phased out in the US. It is no longer manufactured, R-22 air conditioners are no longer built, and R-22 reserves can’t be used to repair old equipment. We recommend anyone who still had an R-22 air conditioner (possible if the unit was installed before 2010) to have it replaced with an R-410A one.

Refrigerant is still developing, and the eventual replacements for R-410A are just on the horizon…

Kilowatt Heating, Air Conditioning and Electrical serves Los Angeles and the San Fernando Valley. Call us when you need top service for your air conditioning in Studio City, CA.

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