The latest technical tests conducted by the Federal Agency for the Environment indicate that tetrafluoropropene or HFO-1234yf is suitable as a refrigerant for automotive air conditioning systems. Both of these refrigerants meet both the requirements of the automotive industry and the EU directives, but the global warming potential (GWP) of these two refrigerants is higher than that of carbon dioxide refrigerants.
Starting on January 1, 2011, automakers must reduce emissions from automotive air conditioning systems. In order to meet EU Directive 2006/40/EC, the international automobile manufacturing industry plans to use the chemical refrigerant tetrafluoropropene in the future. This material will replace the now commonly used refrigerant HFC-134a. German car manufacturers also started the same action in May 2010. However, carbon dioxide, as a refrigerant, has a lower global warming potential than tetrafluoropropene and has the advantage of being flammable, low in cost, and having a good cooling effect. In addition, carbon dioxide refrigerants do not produce any degradation products.
The Federal Institute of Materials Testing conducts a risk test of the use of tetrafluoropropene refrigerants. In the event of a vehicle fire, tetrafluoropropene produces hydrofluoric acid that is toxic and highly corrosive. Tetrafluoropropene itself is also highly flammable. When the metal surface temperature reaches 350°C, high concentrations of hydrofluoric acid are generated even if no chemical combustion occurs. At this temperature, the car can be in operation, such as exhaust pipes and catalytic converters.
Mr. John Henry, chairman of the UBA, said: "The selection of tetrafluoropropene refrigerants may be a relatively simple solution for the air-conditioning market and the global market. However, in terms of climate protection, this is not the best. If you are considering environmental and technical considerations, using carbon dioxide refrigerants may be a more sensible option."

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