USA: The latest SAE cooperative research project (CRP1234) into the safety of R1234yf in car air conditioning systems has confirmed that the risks are still very small compared to the risks of a vehicle fire from all causes and well below risks that are commonly viewed as acceptable by the general public.
The latest CRP was carried out in response to Daimler's tests last year which suggested that R1234yf posed a greater risk of vehicle fire than was estimated by the previous CRP1234 analysis.

The latest results are based on two new fault tree scenarios to consider the possibility of an individual being unable to exit the vehicle due to a collision or a non-collision event that involves a refrigerant/oil release, the refrigerant/oil being ignited and the fire propagating. The fault tree analysis is said to have examined average risks across the entire global fleet and used a number of conservative assumptions to ensure that the final risk estimate would be more likely to overestimate rather than underestimate actual risks.

Tests are said to have shown that dangers posed by R1234yf are nearly six times lower than the current risk of vehicle fires due to all causes and also well below other risks accepted by the general public. The current overall risk of occupant exposure to adverse events based on R1234yf usage is on the same order of magnitude as that estimated in the prior work of CRP1234. Therefore, the conclusions of the former CRP risk assessment are still valid: risks are still very small compared to the risks of a vehicle fire from all causes and well below risks that are commonly viewed as acceptable by the general public.

The OEMs involved in the new CRP - Chrysler/Fiat, Ford, General Motors, Honda, Hyundai, Jaguar Land Rover, Mazda, PSA, Renault and Toyota - are all said to have agreed with the conclusions.

Significantly absent from the new CRP team were the German car manufacturers who continue to shun the use of 1234yf in favour of R134a. According to latest information Daimler has produced 46,817 cars filled with R134a since January, in direct contravention of the European MAC directive.