In a recent paper (Eremin et al., 2017), the authors investigated the opposing influence of various fire suppressants based on the differences in the effects of halogenated hydrocarbons on the ignition of various combustible mixtures. It was shown that all of the additives do not suppress, but some accelerate the ignition of methane/oxygen mixtures. At the same time, these additives suppress the ignition of hydrogen/oxygen mixtures, and the suppression efficiency increases from fluorine to chlorine and bromine compounds. The purpose of this work is to further study the effectiveness of suppressing the ignition of hydrogen/oxygen mixtures by iodine-based additives, namely, CF3I and C3F7I. The results of the experiments show that these additives are the most effective suppressors of hydrogen ignition.