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| accessdate =2006-01-19 }}</ref> It has insignificant ozone depletion potential ([[ozone layer]]), significant [[global warming]] potential ([[Global warming potential|GWP<sub>100</sub>]] = 1300) and negligible acidification potential ([[acid rain]]). 1,1,1,2-Tetrafluoroethane is slowly converted to [[trifluoroacetic acid]] through a [[Radical (chemistry)|radical]] [[reaction]] in the upper [[atmosphere]] and leads to a detectable amount of several ng/L in [[acid rain]].<ref>{{cite journal| author= von Sydow L, Grimvall AB, Borén HB, Laniewski K, Nielsen AT |title=Natural Background Levels of Trifluoroacetate in Rain and Snow|journal=Enviro Sci Technol |year=2000|pages=3115–3118|volume=34|doi=10.1021/es9913683}}</ref> |
| accessdate =2006-01-19 }}</ref> It has insignificant ozone depletion potential ([[ozone layer]]), significant [[global warming]] potential ([[Global warming potential|GWP<sub>100</sub>]] = 1300) and negligible acidification potential ([[acid rain]]). In fact the top climate scientist at NASA, James Hansen, has advanced an alternative view of global warming wherein he argues the of 0.74±0.18°C rise in average global temperatures over the last 100 years has been driven mainly by greenhouse gases ''other'' than carbon dioxide.<ref>http://www.pnas.org/cgi/content/full/97/18/9875</ref> 1,1,1,2-Tetrafluoroethane is slowly converted to [[trifluoroacetic acid]] through a [[Radical (chemistry)|radical]] [[reaction]] in the upper [[atmosphere]] and leads to a detectable amount of several ng/L in [[acid rain]].<ref>{{cite journal| author= von Sydow L, Grimvall AB, Borén HB, Laniewski K, Nielsen AT |title=Natural Background Levels of Trifluoroacetate in Rain and Snow|journal=Enviro Sci Technol |year=2000|pages=3115–3118|volume=34|doi=10.1021/es9913683}}</ref> |
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==Safety== |
==Safety== |
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1,1,1,2-Tetrafluoroethane, also called simply tetrafluoroethane, R-134a, Genetron 134a, Suva 134aorHFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to R-12 (dichlorodifluoromethane), but without its ozone depletion potential. It has the formula CH2FCF3, and a boiling point of −26.3 °C (−15.34 °F).
1,1,1,2-Tetrafluoroethane is an inert gas used primarily as a "high-temperature" refrigerant for domestic refrigeration and automobile air conditioners. Other uses include plastic foam blowing, as a cleaning solvent and as a propellant for the delivery of pharmaceuticals (e.g. bronchodilators), gas dusters, and in air driers, for removing the moisture from compressed air. Moisture present in compressed air has a harmful effect on pneumatic systems. Tetrafluoroethane has also been used to cool computers in some overclocking attempts. It is also commonly used as a propellant for airsoft airguns.
Recently, R-134a has been subject to use restrictions due to its theorized contribution to climate change. In the EU, it will be banned as from 2011 in all new cars[1]. SAE (International, an auto engineers association) has proposed HFC-134a to be best replaced by a new fluorochemical refrigerant HFO-1234yf (CF3CF=CH2) in automobile air-conditioning systems[2]. California may prohibit the sale of canned HFC-134a to individuals to avoid non-professional recharge of air conditioners. A ban has been in place in Wisconsin since Oct 1994 under ATCP 136 prohibiting sales of container sizes holding less than 15 lbs of refrigerant.[3]
R-134a first appeared in the early 1990s as a replacement for Dichlorodifluoromethane (R-12), which has significant ozone depleting properties.[4] R-134a has been atmospherically modeled for its impact on depleting ozone and as a contributor to global warming. Research suggests that over the past 10 years the concentration of 1,1,1,2-tetrafluoroethane has increased significantly in the Earth's atmosphere, with a recent study revealing a doubling in atmospheric concentration between 2001–2004.[5] It has insignificant ozone depletion potential (ozone layer), significant global warming potential (GWP100 = 1300) and negligible acidification potential (acid rain). In fact the top climate scientist at NASA, James Hansen, has advanced an alternative view of global warming wherein he argues the of 0.74±0.18°C rise in average global temperatures over the last 100 years has been driven mainly by greenhouse gases other than carbon dioxide.[6] 1,1,1,2-Tetrafluoroethane is slowly converted to trifluoroacetic acid through a radical reaction in the upper atmosphere and leads to a detectable amount of several ng/L in acid rain.[7]
Contact of tetrafluoroethane with flames or hot surfaces in excess of 250 °C (482 °F) may cause vapor decomposition and the emission of toxic gases including hydrogen fluoride and carbonyl halides.[8] Tetrafluoroethane itself has an LC50 (lethal concentration for 50% of subjects) in rats of 1,500 g/m³, making it relatively non-toxic. However, its gaseous form is denser than air, and will displace air in the lungs. This can result in asphyxiation if excessively inhaled.[9][10]
Aerosol cans containing tetrafluoroethane, when inverted, become effective freeze sprays. Under pressure, tetrafluoroethane is compressed into a liquid, which upon vaporization absorbs a significant amount of thermal energy. As a result, it will greatly lower the temperature of any object it contacts as it evaporates. This can result in frostbite when it contacts skin.
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