Hydrogen(H₂) is used in the semiconductor industries, and some oxidizing gases such as fluoride(F₂) and chlorine trifluoride(ClF₃) are also used. As F₂and ClF₃ are highly oxidizing gases, it were supposed to react vigorously with H₂. In this study, the flammability limit of F₂/H₂/Ar and ClF₃/H₂/Ar mixtures were investigated experimentally. As a result, it was found that the diluted F₂ gas could be spontaneously ignited as compared to ClF₃ mixture gas while being mixed with the diluted H₂gas. However, ClF₃ diluted gas was not able to ignite spontaneously except for an electric spark. And the combustion characteristics and reaction kinetics were shown at the different diluted gases by the flammability diagram analyses between the F₂/H₂/Ar and ClF₃/H₂/Ar.