Refrigerant Gases

A refrigerant is a compound used in a heat cycle that reversibly undergoes a phase change from a gas to a liquid. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants but they are being phased out because of their ozone depletion effects.

 

Other refrigerants include ammonia, sulfur dioxide, carbon dioxide and non-halogenated hydrocarbons such as methane. The ideal refrigerant has good thermodynamic properties, is unreactive chemically, and safe. The desired thermodynamic properties are a boiling point somewhat below the target temperature, a high heat of vaporisation, a moderate density in liquid form, a relatively high density in gaseous form, and a high critical temperature.

 

Since boiling point and gas density are affected by pressure, refrigerants may be made more suitable for a particular application by choice of operating pressure. These properties are ideally met by the chlorofluorocarbons.

 

Until concerns about depletion of the ozone layer arose in the 1980s, the most widely used refrigerants were the halomethanes R-11, R-12 and R-22.

 

Synonyms		CFC (chlorofluorocarbon), HCFC (hydrochlorofluorocarbon), HFC (hydrofluorocarbon)
CAS No.		Refer to specific compound.
		e.g. HFC R134a (1,1,1,2-Tetrafluoroethane): 811-97-2
Chemical formula		Refer to specific compound.
		e.g. HFC R134a (1,1,1,2-Tetrafluoro ethane ): CH2CF3
Vapour density		>1 (air = 1)
Safe Work Australia ES	TWA	Refer to specific compound.
		e.g. R134a (1,1,1,2-Tetrafluoroethane): 1,000 ppm
	STEL
Flammable limits	LEL
	UEL
Equipment group
Temperature classification
Chemical/physical properties		A group of gases used for refrigeration applications, generally being non-toxic, non-flammable, non-corrosive and having the desirable thermodynamic properties of a good refrigerant.
Hazardous properties		Although reasonably safe to use in the workplace, CFCs were found to have a deleterious effect on the Earth’s UV protective ozone layer so their use has been banned and they are no longer manufactured. HFCs and HCFCs are still used as a replacement but as they are potent greenhouse gases (strong absorbers of infrared radiation), their use is carefully controlled and regulated.
		Although non-flammable, decomposition at high temperatures may release toxic gases such as hydrogen chloride, hydrogen fluoride etc.
Occurrence/Uses		Apart from refrigeration, some of these substances find use as synthetic foam blowing agents, industrial solvents and aerosol propellants.
Detectors available		Photoacoustic Infrared (0–1,000 ppm)
Suggested alarm levels