Flammability limits of multi-fluorinated compounds

Flammability limits were measured for a number of multi-fluorinated compounds in a 12 L spherical glass vessel. It was found that the saturated multi-fluorinated compounds with F substitution rate larger than 0.625 are non-flammable. Those with F substitution rate of 0.625 may or may not be flammable depending on the molecular structure and the humidity condition. A numerical analysis was carried out on the observed values of flammability limits for some 120 compounds including the multi-fluorinated ones. For multi-fluorinated compounds with F substitution rate of 0.6 or less, the flammability limit values can be explained reasonably well by the analysis. It is to be noted, however, that even for the non-flammable multi-fluorinated compounds the numerical analysis tends to predict them to be flammable.