Worthwhile applications for laser beam ablation in the macro range re found wherever hard materials, short process times and high precision are required. The laser beam ablation of thick-walled metals is gaining attention, especially in the field of industrial dismantling and the elimination of hazardous substances. This requires a high degree of flexibility, both in the machining process and in terms of mobility with regard to the place of use. Special attention is given to situations where sensitive, contaminated or explosive materials are behind the metal walls to be removed. It must be ensured that these substances are not influenced critically under any circumstances. In this context, a process of removing hazardous substances in closed cavities is developed. To prevent risks by initiating a reaction with these dangers, the thickness of the 10 mm plates is reduced without applying mechanical force and without exceeding a critical temperature. The volumetric rates of laser beam ablation have hitherto been severely limited by the requirement of high surface finishes. This article shows that the volumetric rates can be significantly increased by means of an adapted process strategy and an off-axis process gas control. Despite high volumetric ablation rates and the associated high laser energy, it is ensured that there is no danger to the hazardous substances. The critical temperature of 300°C which is several times lower than the melting temperature of the sheath, is not exceeded at the rear surface of the sheet metal. Results are presented which show how different process parameters affect the ablation depth and the workpiece temperature.