Not all accidental releases of flammable gases and vapours create explosions; most releases do not find an ignition source and of those that do ignite, most of them generate low or moderate overpressure only (deflagrative combustion). However, when certain conditions are satisfied, deflagration to detonation transition (DDT) can occur followed by stable detonation. A detonation is a rare event; however, it is a worst-case accidental event. Overpressures in detonation are much higher compared to deflagration. In addition, detonation does not stop at the edge of the congestion, as in case of deflagrations, but detonation continues through the entire flammable cloud. Items within the detonating cloud are destroyed or rendered unusable.
An intense vapour cloud explosion (VCE) occurred at the Buncefield fuel storage site in 2005. Extensive research into this incident revealed beyond doubt that detonation had taken place in the vapour cloud. Alternative mechanisms were considered and dismissed because they did not adequately explain the observed damage. Unique data were collected on the impact of blast on items of industrial plant, vegetation and vehicles. Combined with advances in fundamental knowledge of detonation science and large-scale tests on detonations, these new insights have allowed a comprehensive interpretation of the multitude of previous accidents involving intense vapour cloud explosions. The review identifies several past industrial accidents in which detonation was the cause of major destruction and loss of life. The new insight presented should help safety engineers to comprehend aspects of explosion hazards, to prepare and to optimise safety management procedures to minimise the detonation risk.