In accidental gas explosions, blast waves propagate toward the surroundings after the bursting of the vessel or building, in which gas explosions occur. The strength of the blast wave depends not only on explosion behavior, but also bursting strength. This phenomenon has not been thoroughly examined. In the present experimental study, blast waves from hydrogen-air deflations in plastic vessels with various strengths were measured and flame behavior was recorded by digital high-speed video cameras. The measured peak overpressure and impulse of blast waves were compared with those of blast waves from unconfined gas explosions. Furthermore, these were compared with the calculated values of blast waves from bursting vessels without combustion reaction. Peak overpressure appeared when the vessels burst. The peak overpressure and impulse depended on the strengths of vessels, and were larger than those from unconfined gas explosions and bursting vessels without combustion reaction.