The current practice in industry in vapour cloud explosions (VCE) assessment is to assume that all VCEs are deflagration. This practice has been in place for nearly three decades. Development of assessment methods has been focussed on predicting the consequence of a deflagration: from simple empirical models to complex models based on computational fluid dynamics. The severity of a deflagration is limited by the amount and extent of congestion such as those present in onshore process plants or on offshore oil and gas facilities. There have been experiments showing severe deflagrations can transit to detonation. Recent VCE accident investigations on Buncefield in the UK and Jaipur in India concluded that the VCEs involved detonation. There could be more; re-evaluation of past accidents is underway and the indication is that past VCEs classified as deflagration could be detonation. The inclusion of detonation in hazard and risk assessment would identify new escalation potentials and identify critical buildings impacted. This knowledge will allow a more effective management of this hazard.
