The aim of the paper is to reveal specifics of the blast wave loading at walls during an accident volume explosion in the industrial vented premises. The external problem of the blast dynamics is investigated by the method of numerical simulation. Analysis reveals the following specific effects, which are generally inherent to the blast impact process: amplification of the cumulated energy in corners by powerful flow behind Mach stem and then after its reflection from the opposite wall; prolonged rarefied action of vortex at the wall edge; intense local thermal and gas-species mixing in a vortex funnel, which can boost up the re-ignition process; interaction at the outer wall face of the shock waves diffracted at the multigate wall edges. The latter three insist on the necessity of the outer flow computing in the region adjacent to premises in order to obtain correct assessments of the blast loads at walls. Transient distributions of the pressure force impulse and overpressure along the premises perimeter are calculated, which clearly reflect the influence of the found gasdynamic effects. The transient fields of the dynamic parameters are processed in the video format, as well. It is concluded that the revealed specifics must be taken into account in the blast mitigation measures, damage assessments and should be reflected in the dynamic criteria of the wall fracture. (C) 2017 Elsevier Ltd. All rights reserved.