Mechanical refrigeration appeared in the middle of19th century. Jacob Perkins made the first practical machine in 1834. It uses ether as refrigerant and is a vapor compression system. Carbon dioxide (CO2) and ammonia (NH3) were used as refrigerants for the first time in 1866 and 1873 respectively. Other chemicals, including chemical cyanide (petroleum ether and naphtha), sulfur dioxide (R-764) and methyl ether, have been used as refrigerants for vapor compression. Its application is limited to industrial processes. Most foods are still preserved with ice collected in winter or made in industry.

At the beginning of the twentieth century, refrigeration system began to be used as an air-conditioning means for large buildings. Meilan Building in San Antonio, Texas is the first fully air-conditioned high-rise office building.

1926, Thomas Miccini developed the first CFC machine using R- 12. CFC family (chlorofluorocarbons) is nonflammable, nontoxic (compared with sulfur dioxide) and has high energy efficiency. The machine started commercial production on 193 1 and soon entered the family. Willis carrier invented the first commercial centrifugal refrigerator, which initiated the era of refrigeration and air conditioning.

In 1930s, a series of halogenated hydrocarbon refrigerants appeared one after another, and DuPont named them Freon. These substances have excellent properties, are non-toxic and non-flammable, can adapt to different temperature regions, and significantly improve the performance of refrigerators. Several refrigerants have become very common in air conditioners, including CFC- 1 1. CFC- 12。 CFC- 13。 CFC- 1 14 and HCFC-22.20, which were used since 1950s. Non-boiling refrigerants were used in the 1960s.

The use of the above refrigerants in the air conditioning industry has developed from infancy to a multi-billion dollar industry. To 1963, these refrigerants account for 98% of the total output of organic fluorine industry.

By the mid-1970s, concerns about the thinning of the ozone layer surfaced, and chlorofluorocarbons may be part of the reason. This led to the adoption of 1987 Montreal Protocol, which requires the phase-out of CFCs and HCFCs. The new solution is to develop HFC series and play the main role of refrigerant. The HCFC series will continue to be used as a transitional scheme and will be phased out.

In the1990s, global warming posed a new threat to life on earth. Although there are many factors leading to global warming, refrigerants are included in the discussion because of the huge energy consumption of air conditioning and refrigeration (building energy consumption in the United States accounts for about 1/3 of the total energy consumption) and many refrigerants are greenhouse gases themselves. Although ASHRAE Standard 34 classifies many substances as refrigerants, only a few substances are used in commercial air conditioners.