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A grease that does not burn promises to help prevent lethal fires in tunnels of the kind that struck the Los Angeles Metro tunnel this summer, seriously injuring several people.

Developed by Jim Washbourne of Oxford Brookes University's civil engineering department, the grease could now be used in major tunnel construction projects currently under way. The Jubilee Line Underground extension to the London Docklands and the Heathrow Express tunnel, connecting the airport to London's Paddington station, could both benefit.

He explains that flammable greases are currently being widely used in combination with seals to make the gap between the tunnel lining and tunnel boring machine watertight. When the seals are repaired or replaced, water is often kept at bay by pumping compressed air into the tunnel workings. Workers burn away worn seals with oxyactylene torches and in this oxygen-rich atmosphere, the grease can ignite with lethal consequences.

Mr Washbourne's solution is a non-flammable grease made up of water and minerals suspended in wax. He says that globally, 3,500 kilometers of tunnel are dug every year for drainage, sewage, services, roads and rail. Tunnelling accounts for the world's biggest use of grease. "As the earth's surface becomes more crowded there is even more need for tunnels and unless we replace inflammable tunnel grease soon, fires will claim the lives of more workers."