[LGAFF]

This is interesting

According to the press release, numerous tests have been performed on R-1234yf by automakers and independent agencies alike with no negative effects, but Daimler says that is has found a certain scenario where the refrigerant can leak at high pressures and ignite. Daimler found that in severe head-on collisions, the refrigerant line can break and spray R-1234yf onto the exhaust system causing a fire. It isn't certain how severe the fires were, but as a precautionary measure, Daimler says that it will continue to use R-134a in all of its cars.

Looking at independent tests performed by DuPont and Honeywell, the results showed that R-1234yf is "very difficult to ignite with electrical spark" and this refrigerant "shows [the] same flammability behavior as R-134a." This latter result showed ignition against a metal plate with a temperature above 900 degrees Celsius with the ignition of both refrigerants in this scenario attributed to the existence of PAG oil used in automotive air conditioning systems; the tests did not say if the refrigerant was pressurized as it was in the Daimler tests.