The inhibition effectiveness of CF3Br (halon-1301) is found to be superior to nitrogen as well as an environmentally safe hydrofluorocarbon, CF3CHFCF3 (FM-200). In order to explain its unique inhibition capabilities, the structure of laminar diffusion flames subjected to various concentrations of CF3Br is computed and analysed. Perfectly stirred reactor calculations for CH4-air-CF3Br mixtures have also been performed. These studies reveal that the catalytic cycle which leads to the recombination of two hydrogen radicals to form H2 may change to another, more effective cycle which consumes one oxygen and two hydrogen atoms to form water. The switch from one cycle to the other depends on the dominant direction of the reaction: H + HBr ⇌ H2 + Br.