This study addresses one of knowledge gapsin hydrogen safety science and engineering, i.e. apredictive model for calculation of deterministic separation distancesdefined bythe parameters ofa blast wave generated by a high-pressure gasstorage tank rupture in a fire. An overview of existing methods to calculate stored in a tank internal(mechanical) energy anda blast wave decayis presented. Predictions by the existing techniqueand anoriginal modeldeveloped in this study, whichaccountsforthe real gas effects and combustion of the flammable gasreleasedintotheair(chemical energy),arecompared againstexperimental dataon high-pressurehydrogen tank rupture in thebonfiretest. The main reasonfor a poor predictive capability of the existing models isthe absenceof combustion contribution to the blast wave strength. The developed methodologyis able to reproduce experimental data on a blast wave decay after rupture of a stand-alone hydrogen tank and atank under avehicle.In this study, the chemical energy isdynamically added to the mechanical energy and is accounted for in the energy-scaled non-dimensional distance. The fractionof the total chemical energy of combustion released to feed the blast wave is 5%2and9%2 howeverit is 1.4 and 30 times larger than the mechanical energy in the stand-alone tank test and the under-vehicle tank test respectively.The model isappliedas a safetyengineering tool to fourtypical hydrogen storage applications,includingon-board vehicle storage tanksand a stand-alone refuelling station storage tank. Harm criteria topeople and damage criteria for buildings froma blast wave are selected by the authorsfrom literature to demonstratethe calculation of deterministicseparation distances.Safety strategiesshouldexclude effectsoffire on stationary storage vessels, and requirethermal protection of on-board storage to prevent dangerous consequences ofhigh-pressure tank rupture in a fire.