International audienceDespite significant progresses in the understanding of the formation and propagation of pressure waves in the open atmosphere in the past decades, experience form past accidents (AZF, Toulouse, 2001, Billy-Berclau, 2003 and even Buncefied 2005) reveals that overpressure levels may be greatly ill estimated. This is obviously a concern when the protection of citizens is concerned. There are some indications that both the topography and weather conditions may play a significant role but this remains rather qualitative and there is a need to clarify such points. In this paper, the results of a preliminary experimental campaign are presented in which up to 500 kg eq TNT was detonated in the open atmosphere and the pressure field measured up to 10 kms