ABSTRACT
This incident was Britain’s largest peacetime explosion to date (HSE 2011, p. 11). Although no one died, there were substantial economic and community impacts, e.g. the two major fuel pipelines to Heathrow and Gatwick airports were also controlled from an adjoining site. The investigation was lengthy and complex. Despite this, the incident was really very simple. At around 05.40 on Saturday 11th December 2005 one very large petrol storage tank at the Buncefield oil storage depot in Hemel Hempstead overfilled. The leak was not noticed in the control room or detected outside before a large petrol vapour cloud had formed. This ignited and exploded just after 06.00. All of the safety barriers failed on the night, including the tank level gauge which stuck so that the associated high-level alarm did not sound in the control room. The final independent high level switch (IHLS) on the tank had not been correctly set, and so also failed to work.
