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CHANNEL TUNNEL SYSTEM USED TO CLEAR SMOKE

ROADS AND BRIDGES

AS GILBERT Degreaves drove his truck into the Mont Blanc tunnel between Italy and France on the morning of March 24, 1999, it would have been impossible for him to know that his journey would have repercussions that would echo around Europe.

According to reports Mr Degreaves was making his way through the 11.6 km-long tunnel when the flashing lights of oncoming motorists warned him of trouble with his load. As he stopped and got out his cab he realised there was a fire on the back of his lorry. Though he would try to fight it, the flames forced him back.

Five days later, af ter the tunnel cooled enough for inspection, the death toll had hit 39, the worst in a history of tunnel fires in the Alps.

In the aftermath steps were taken to avoid similar tragedies in the future. Tunnel fire safety codes and regulations were tightened up and new technologies were considered to fight the effects of fires that did occur.

Such technology will be seen in the Holmesdale tunnel in the form of massive Sacarddo nozzle ventilation system.

'The existing jet fans were nearly 25 years old and could only be used for clear ing pollut ion. This new system can remove smoke and hot gasses in the event of a fire, ' says Russell Williams of Mouchel Parkman.

This was one of the lessons that was learned from the Mont Blanc disaster, where the majority of the deaths were caused not by the heat of the fire but by the fumes.

'Vehicles ahead of the fire are alright; they can drive away f rom it. It is the vehicles behind that are in danger. The fans can blow any smoke away from them, ' says Mr Meadowcroft.

The Sacarddo system, which uses giant nozzles above the tunnel end to suck air in and force it down the bore, was chosen because there was not space inside the tunnel for jet fans. The system has already proved its worth on the Channel Tunnel Rail Link, where it helped control smoke during a fire last August