<P> Early mechanical refrigeration systems employed sulfur dioxide, methyl chloride and ammonia . Being toxic, sulfur dioxide and methyl chloride rapidly disappeared from the market with the introduction of CFCs . Occasionally, one may encounter older machines with methyl formate, chloromethane, or dichloromethane (called carrene in the trade). </P> <P> Chlorofluorocarbons were little used for refrigeration until better synthesis methods, developed in the 1950s, reduced their cost . Their domination of the market was called into question in the 1980s by concerns about depletion of the ozone layer . </P> <P> Following legislative regulations on ozone depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), substances used as substitute refrigerants such as perfluorocarbons (FCs) and hydrofluorocarbons (HFCs) have also come under criticism . They are currently subject to prohibition discussions on account of their harmful effect on the climate . In 1997, FCs and HFCs were included in the Kyoto Protocol to the Framework Convention on Climate Change . In 2006, the EU adopted a Regulation on fluorinated greenhouse gases, which makes stipulations regarding the use of FCs and HFCs with the intention of reducing their emissions . The provisions do not affect climate - neutral refrigerants . </P> <P> Refrigerants such as ammonia (R717), carbon dioxide and non-halogenated hydrocarbons do not deplete the ozone layer and have no (ammonia) or only a low (carbon dioxide, hydrocarbons) global warming potential . They are used in air - conditioning systems for buildings, in sport and leisure facilities, in the chemical / pharmaceutical industry, in the automotive industry and above all in the food industry (production, storage, marine shipping, retailing). In these settings their toxicity is less a concern than in home equipment . </P>

What type of lubricant is used with hcfcs