In this study, the pressure-temperature explosion limits of H-2/CO/O-2/CO2/H2O mixtures are analyzed computationally and theoretically. The result indicates that with the increase of H2O and CO2 mole fractions, the explosion temperatures are increased around all the three explosion limits. Furthermore, the increase of the explosion temperature is higher with the addition of H2O compared with the addition of CO2 near the second explosion limit. In addition, the increase of the explosion temperature near the first and third explosion limit is almost the same for the addition of these two inter gases. The single-limit expression analysis shows that the first explosion limit is mainly controlled by the changing of the oxygen concentration with the addition of inert gas; the changing of the second explosion limit is caused by the changing of the reaction rate of H + O-2 (+M) -> HO2 (+M), which is indirectly through the Chaperon efficiency of the third body recombination reaction, and the effect of inert gas addition on the third explosion limit is mainly caused by the changing of the hydrogen concentration. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.