[15] Added safety measures are needed for when fuel does escape, mainly to prevent it forming a flammable vapour and stop pollutants from poisoning the environment.

[3][17] Hertfordshire police and fire services and the member of parliament for the area, Mike Penning, said that there were seven fuel tanks on the site which, as of 14:00 on 12 December, had not been affected.

[10] Around 150 firefighters were called immediately to the incident, and began tackling the blaze at 08:20 on the morning of 11 December, putting in containment measures before applying a large quantity of foam.

[3][6] Plans had been in place to start using foam at midnight on 11 December, but were delayed by last-minute concerns over possible pollution of local rivers and underlying water sources.

[21] This led to the M1 motorway being closed again; the public exclusion area was widened, and firefighters were temporarily withdrawn until the risk posed by the threatened tank could be assessed.

Further damage occurred to one of the storage tanks in the early hours of Tuesday morning, causing firefighters to be withdrawn once again, but operations resumed at 08:30.

[21] Bronze command – operations on the ground – was visited by the Bishop of St Albans, the local vicar, and the industrial chaplain supporting the fire crews, to see how they were coping.

The entire gold command operation, involving many agencies as well as all the emergency services, was run from Hertfordshire Constabulary's headquarters in Welwyn Garden City, some distance from the fire.

Firefighters were of the view that extinguishing it would leave the risk of petroleum vapour re-igniting or exploding, so it would be better to allow the fire, which was well contained, to burn itself out.

[5][16] The black smoke cloud, which was visible from satellite photographs, drifted at a high altitude, around 9,000 feet (2,700 m), towards Reading and Swindon, and could be seen across much of South East England.

[20] To investigate the smoke cloud the Facility for Airborne Atmospheric Measurements, a research aircraft operated jointly by NERC and the Met Office, made two flights on 12 and 13 December.

Carbon monoxide, nitrogen oxides and ozone concentrations were found to be low with soot particles being the major component in the cloud.

[3][20][23] Hertfordshire Constabulary advised people who had houses with smashed windows to seek refuge with friends or family nearby if possible.

[18] Total, the operator of the Buncefield depot, set up a helpline for people whose properties had been damaged by the explosion, and called in local authorities and the Salvation Army to provide accommodation or other help.

[17] Hemel Hempstead MP, Mike Penning accused the government of changing the rules to suit the situation in which PFOS levels in drinking water in the area may rise in the future.

[33][34] An initial progress report by the Major Incident Investigation Board on 21 February 2006 did not go into the causes of the explosion, but summed up the event and the immediate reaction from the emergency services.

Starting at 19:00 on the evening of 10 December 2005, Tank 912, towards the north west of the main depot, was filled with unleaded petrol – from the Coryton Refinery located in Essex, England.

[18] An initial trial concluded on 23 May 2008 when Mr Justice David Steel issued a summary judgment after hearing that both Total and Hertfordshire Oil Storage Ltd (HOSL) had agreed that negligence was the cause.

[7][19] In the main trial, Total UK claimed that the duty supervisor at the time was responsible for the explosion, but refused to admit either civil or criminal liability for the incident.

The Control of Major Accidents and Hazards Regulations are jointly enforced by the competent authority which is formed of the Environment Agency and the Health and Safety Executive.

In April 2010, the five companies accused of causing the explosion faced a criminal prosecution brought by the Health and Safety Executive and the Environment Agency.

Two defendants, Total UK and British Pipeline Agency Limited, had already pleaded guilty to offences under the Health and Safety at Work Act.

[5][6][7][8] The seat of the fire, and the worst damaged section, was "HOSL West", used by Total and Texaco to store a variety of fuels, and the neighbouring British Pipeline Agency area.

Eventually Tank 912 filled up completely, the petrol overflowed through vents at the top, and formed a vapour cloud near ground level, which ignited and exploded.

[43] The investigation found that the level gauge had stuck at random times after a tank service in August 2005, but it did not concern maintenance contractors or site management.

Tertiary containment (drains and catchment areas to prevent release of spilled chemicals to the environment) also failed, and fuel and firefighting foam entered groundwater supplies.

Site staff did not have control over the flow rates and timing of two of the three inlet sources, meaning that they did not have enough information to properly manage the storage of incoming fuel.

An anniversary service was held in Holy Trinity Church Leverstock Green on Sunday, 10 December 2006, at which the Bishop of St Albans spoke, calling again for a full public inquiry, for assurances that the local hospital would maintain its accident and emergency department, and for the community to continue to build on good and new relationships formed because of the blast.

[45] BP is exploring plans for the future use of this part of the site, and has indicated a number of priorities, including the reopening of the fuel pipelines to Heathrow.

[47] On the roundabout at the entrance to Hemel, the "Phoenix Gateway" sculpture was designed by Jose Zavala to symbolize the recovery of the town from the Buncefield oil depot explosion.