An extensive program of experimental work has been performed at the TNO Prins Maurits Laboratory on the quenching of hydrogen/air flames in various geometries on a medium scale by partial inertization. The main parameters investigated were the composition of the gas mixture and the measure of obstruction of the flow field in order to vary the degree of turbulence. The fuel concentration was varied between equivalence ratios of 0.25 and 1.00. The influence of carbon dioxide and nitrogen addition was investigated during separate trials. Both inert gases were added up to 30 vol% in the various geometrical arrangements. On the basis of an initial study by Sherman et al., a basic methodology has been developed for the estimation of explosion effects of hydrogen/air/inert mixtures. The method is a simplification of the actual processes during the experiments and is therefore only indicative. It is intended to be used by those who are not expert in the field. Knowledge of the gas composition can be used to safety advise applications on a large scale, on the basis of four conservatively chosen regimes of explosion severity.