The recent set of large scale experiments at Spadeadam produced a considerable amount of data which consisted of sets of pressure-time histories recorded at very high sampling rates during the explosion events. In many experiments, very high over pressures were measured, however, these high pressure peaks were of very short duration. In this paper, we examine characteristics of pressure-time data from large scale tests and present the results in three different forms, and show that the application of headline maximum over-pressure values to assess structural response is not applicable. The response characteristics of the target structure must be included in the definition of maximum over-pressure for structural assessment. While work is still ongoing at BP Amoco, preliminary results are presented in this paper. Our initial finding would indicate that (a) depending on the structure of interest, very different conclusions could be drawn concerning the relative severity of various explosion events and the benefits of mitigation measures, and (b) it is potentially dangerous to arbitrarily strengthen structures to withstand these high peak over-pressures. (C) 2000 Elsevier Science Ltd. All rights reserved.