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Chlorodifluoromethane is a chloroform chemical produced through the chlorination of methane and is primarily used as a refrigerant compound as well as in the production of polystyrene and polyurethane foam plastics. Another common industry term for chlorodifluoromethane is refrigerant 22 (R-22) or hydrochlorofluorocarbon 22 (HCFC-22). Hydrochlorofluorocarbon compounds are intermediate compounds being used by developing nations in the phase out of chlorofluorocarbons (CFCs), due to their energy efficiency and low toxicity. HCFC compounds still pose some risk to the depletion of the Earth's ozone layer and as a greenhouse gas, however, and worldwide production of R-22 is on the decline as it is replaced by safer refrigerants such as R-134a. In the United States as of 2011, production of HCFC-22 is scheduled to be completely halted in the year 2020.
The Chemical Abstracts Service (CAS) listing of the American Chemical Society (ACS) categorizes the chemical as chlorodifluoromethane — CAS number 75-45-6, with the chemical formula of CHClF2. It is a colorless gas with many synonyms in industry such as difluorochloromethane, and is considered a stable organic compound. It has a low boiling point as a compressed liquid of -41.44° Fahrenheit (-40.8° Celsius) and an even lower melting point as a solid of -230.8° Fahrenheit (-146° Celsius).
Refrigerant chemicals like CFCs and HCFCs tend to be largely inert and long-lasting compounds, which is what enables them to survive for extended periods in industrial machinery or nature. Once outdoors, they slowly drift into the upper atmosphere over the course of a decade or more. When they reach a high enough altitude, ultraviolet radiation from the sun and chemical interaction with the atmosphere breaks them down into greenhouse gas and ozone-depleting compounds.
The material safety data sheet or chlorodifluoromethane MSDS also suggests that they pose some health hazards. When inhaled in concentrations of 50,000 parts per million or greater, they can affect the central nervous system and create irregular heartbeats and could cause death. They also have the potential to cause damage to the liver, kidneys, and blood in high concentrations.
HCFC compounds were introduced as a short-term solution to replace CFCs. Ozone depletion chemical production of CFCs peaked globally in 1987-1988, and, since the introduction of HCFC compounds at the time, worldwide consumption of CFCs has fallen by 75% as of 1996. Despite this and the fact that HCFCs, like chlorodifluoromethane, are 98% less ozone-depleting than CFCs were, their reduced ability to deplete the ozone layer is still seen as unacceptable long- term.
In 1987, an international agreement known as the Montreal Protocol created a timetable for the phasing out of ozone-depleting chemicals such as chlorodifluoromethane gas. Since the R-22 compound is the most widely used refrigerant in commercial cooling and heating systems in the industrialized world, it is a major undertaking to remove it from society entirely. All new refrigeration equipment installed in buildings as of 2010 must contain R-410A instead of R-22, and R-134a is being used in automotive applications to replace chlorodifluoromethane. The Montreal Protocol was signed by 196 nations, and its provisions for the phasing out of chlorodifluoromethane are expected to return the ozone layer to its natural state by the year 2050.