The results of large-scale experiments on combustion of local hydrogen-air mixtures in a chamber of 20 m(3) volume are presented. It has been shown that, for mixtures with a relatively high laminar burning velocity, containing 30% (vol.) hydrogen in air, the explosion pressure and the explosion pressure rise rate decrease more rapidly in the case where the vent area is located in the vicinity of a local combustion mixture. For mixtures with a relatively low laminar burning velocity, containing 10% (vol.) hydrogen in air, the more rapid reduction of an explosion pressure was observed at the location of a vent area far from a local combustible mixture. The mutual influence of repeated obstacles and gasdynamic disturbances, caused by a gaseous mixture motion to a vent area, on the intensification of the local mixtures combustion has been investigated.