Most researches on blast waves generated from gas explosions were focused on open space gas explosions. However, accidental gas explosions often occur in confined spaces and the blast waves generate from bursting vessels as a result of pressure increase raised by gas explosions. In this experimental study, blast waves from bursting plastic vessels, in which gas explosions occurred, were measured. The flammable mixtures were hydrogen-air mixtures at several equivalence ratios and stoichiometric methane-air mixture. Blast waves generated from bursting vessels were measured. The overpressures of blast waves were generated by venting high pressure gas in the vessel and volumetric expansion with combustion reaction. The measured intensities of blast waves were compared with the calculated values of blast waves from bursting vessel by high pressure gas without combustion reaction. The measured intensities of blast waves were larger than the calculated values by high pressure bursting without combustion reaction. The intensities of blast waves by the explosions of hydrogen-air mixtures were much larger than that of methane-air mixture.