Ignition energy effects of concentration of mixed gas In closed cylindrical vessel(1, 832㎤) are studied. The ignition energy ranged from 25 Joule to 110 Joule, and hidrogen and methane gases were used for flammable gas at stoichiometric condition with oxygen gas and nitrogen gas (N2) was for inert gas, which concentration was maximum 60% . The explosion pressure, temperature, concentration of product gases were calculated. It is found that - The explosion pressure and explosion velocity increase with ignition energy. - The gradience of explosion velocity with ignition energy is steeper than explosion pressure. - The results of calculation are similiar with results of experiment. - NOx is not serious product gas for methane and hydrogen gas, but CO is serious at certain concentration for methane in asphyxiation.