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Aug 7, 2006 2:20 PM

The US Chemical Safety and Hazard Investigation Board (CSB) has issued a courtesy notice related to level switches on storage tanks after a major explosion and fire at a storage and terminaling facility in England December 11, 2005. The United Kingdom Health and Safety Executive issued a safety alert after conducting an investigation of the incident.

"The report indicates that the explosion probably resulted from the ignition of a vapor cloud formed when a tank containing unleaded gasoline overflowed," CSB said. "One aspect of the investigation is the operation of the 'ultimate high level switch' on the tank. It is part of the system designed to prevent the tank from overflowing."

The United Kingdom agency safety alert includes a check list to aid in identifying and testing the switches. Although these types of level switches are manufactured in the United Kingdom, the agency believes that they may have been supplied to customers throughout Europe and North America. The safety alert is primarily for the attention of those companies operating oil/fuel storage facilities. However, it may also be relevant to other sites storing hazardous substances in large tanks where level gauges are used, CSB said.

The fire and explosion at the Buncefield petroleum storage depot in Hemel Hempstead in Hertfordshire swept through the surrounding area, causing $2 billion in damage. The blast that preceded the fire registered 2.4 on the Richter scale.