USA: Fresh from announcing new research into the safety of R1234yf as a substitute for R134a in car air conditioning systems, engineers body SAE International is now proposing to re-evaluate the technical aspects of CO2 as an automotive air conditioning refrigerant.
The call comes from SAE International president Frank Klegon in response to a recent press statement attributed to Volkswagen boss Ferdinand Piech that 'CO2 is the right refrigerant'. The comments in German auto magazine website Autobild followed the decision by fellow German manufacturer Daimler to reject 'mildly flammable' R1234yf on safety grounds.
SAE International has invited all automobile manufacturers to join in an industry collaborative effort to fully evaluate the technical aspects of the use of CO2 as an automotive air conditioning refrigerant.
This will probably be good news to many German car manufacturers who originally championed the development of CO2 as the replacement for R134a but fell into line with the rest of the world in accepting R1234yf.
However, the SAE president Klegon, referring to previously published US EPA reports regarding the use of CO2, warned: 'The implementation of CO2 as an automotive refrigerant is not without technical challenges.'
Under its Significant New Alternatives Policy (SNAP) programme published this year, the US EPA found that the use of CO2 posed risks that were lower than or comparable to the risks posed by other acceptable substitutes. However, it specified the use of fittings with specific dimesions to deal with the higher pressure refrigerant. In addition, in the event of a CO2 leak into the passenger area, it placed maximum short term exposure limits of 3% (30,000ppm) averaged over 15 minutes with a ceiling limit of 4% in the passenger breathing zone.
EPA reports have revealed that exposures over 4% (40,000 ppm) CO2 are likely to cause discomfort and signs of intoxication that could impair the driver's response to road and driving conditions, and could create safety and health risks to the passengers.