This study is part of an effort to assess the mechanical effects of an accidental explosion of a gaseous mixture cloud (hydrogen-air in this paper) in an unvented structure and deals with the detonation phenomenon. The aim of this paper is to present and estimate the adequacy of different approaches addressed to dynamic loading approximations. For this purpose, the research is based upon an experimental study at laboratory scale which constitutes the first of the approaches analysed. The experimentation is conducted with respect to the Hopkinson scaling law which allows one to estimate pressure in large-scale geometry. Thereafter, the capabilities of the Autodyn code to predict the pressure loads in confined surroundings are determined. The use of the computational code is a two-step process. Firstly, the incident pressure field is determined by the detonation of the TNT equivalent mass of the gaseous mixture; then the pressure field is introduced in the calculation domain and the interaction with the structure is observed. In addition, the simplified method proposed by Baker is also verified. This paper is an attempt to answer the following question: what is the best safety assessment strategy for the structures subjected to internal blast wave loading? Pressure on the faces of the structure has a complicated evolution, but is thoroughly described in the Autodyn code approach. (C) 2004 Elsevier Ltd. All rights reserved.