A POTENTIALLY lethal gas cloud rolled down a town centre street after "idiot" pranksters opened the valve on a 30,000 litre liquid nitrogen cylinder at Thwaites' Brewery, Blackburn.

Firefighters said the vandals who opened the valve on the liquid nitrogen cylinder in Starkie Street could have been killed when the suffocating gas was released at 8.45pm on Saturday.

When liquid nitrogen is released into the atmosphere, it instantly freezes, creating a dry ice cloud similar to that seen at pop concerts.

Blackburn station officer Tom Davies said: "This was potentially lethal. There was an eight-foot tall wall of dry ice rolling down Penny Street. It looked like something from a Michael Jackson concert.

"But the gas freezes anything in its path and is asphyxiating. If somebody had fallen down in the gas cloud, they wouldn't have got up again.

"This was an extremely dangerous thing to do, and the idiots who did it could have been killed."

Firefighters entered the compound through an unlocked door and shut off the open valve. The gas leak left a one-foot thick coating of ice over equipment in the gas tank compound.

A spokesman for Thwaites said: "This was a very foolish prank. Although the bulk storage tanks are external to the brewery, Thwaites now intends to examine all security around the area to make sure that it is as secure as possible.

"On Saturday nitrogen gas was noticed to be leaking from the storage tank. The fire brigade were notified along with Thwaites' own engineering staff and both attended the incident. "Vandals had broken into the locked compound area surrounding the bulk gas storage tank and opened one of valves to the secondary filling line.

"The evaporation of nitrogen issues a large gas cloud because of its low temperature, but only a small amount of nitrogen was lost.

"The fire brigade successfully closed the valve and stopped the leak. Our engineering staff checked to make sure all was as it should be. Nitrogen is an inert gas which makes up 79 per cent of the atmosphere. But in confined spaces it can be extremely dangerous as it excludes oxygen and can asphyxiate people."

The Health and Safety Executive confirmed that Thwaites had reported the incident and the company was compiling a report.

Converted for the new archive on 14 July 2000. Some images and formatting may have been lost in the conversion.