Hydrofluoroolefins are not as safe to use as they are said to be ...
It is widely used in automobile air conditioners as a refrigerant. According to experts, the widespread use of R1234yf in the world is comparable to the decommissioning of more than 30 million vehicles. Daimler has tested this refrigerant in a head-on collision, in which the refrigerant line breaks and vapors enter the hot compartment of the vehicle's engine, and has shown that R1234yf is flammable and, in the event of a fire, decomposes to form highly corrosive and toxic substances.