This book focuses on the numerical and experimental study of situations resulting from extreme conditions caused by an enclosed or semi-enclosed environment in which explosions occur. Numerical means which is aimed at the damage to structures, e.g. tunnel linings, is a combined method of discontinuous Galerkin (Galerkin - Petrov) and boundary elements (DGBEM). The air flow is described by a combination of the Galerkin - Petrov and the ALE - Arbitrary Lagrangian-Eulerian method.