Flammability limits were measured for a number of olefinic and saturated fluoro-compounds in a 121 spherical glass vessel. The obtained data together with the ones of previous studies have been analyzed based on the F-number scheme of flammability limits. The flammability limits of these compounds have been found to be explained very well by the present scheme of interpretation. The flammability limits are dependent upon distribution of F atoms in a molecule as well as upon F-substitution rate itself. It has been found that -O-CF3 group in a molecule conspicuously decreases the flammability of the compound, while -C-CF3 group does not much. For olefinic compounds, distribution of F atoms around double bonds markedly diminishes the flammability of the molecule. (C) 2009 Elsevier B.V. All rights reserved.