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Zinc-lined pipes suspected in Helsinki theatre blast

Finland's chemicals safety agency called for a ban on the use of zinc-lined pipes in new sprinkler systems in Finland.

Poliisiauto Helsingin kaupunginteatterilla
The explosion occurred in June. Image: Esa Syväkuru / Yle
Yle News

The Safety and Chemicals Agency (Tukes) is recommending that installers avoid using pipes with a zinc lining when they set up new sprinkler systems. The advisory follows an explosion that took place at the Helsinki City Theatre last summer, in which one person was injured.

The blast occurred in the sprinkler centre on the second floor of the Studio Elsa building in Helsinki’s Hakaniemi district. The accident was caused by hydrogen escaping into the air from the pipe system, Tukes said in a statement on Monday. The mixture of hydrogen with the air in the sprinkler room created a flammable mixture, the agency added.

Tukes noted that similar accidents had not previously occurred in Finland, so it was not possible to prepare for it.

Gas the result of corrosion

Tukes said that the hydrogen gas formed when zinc lining the pipes in the sprinkler system oxidised in a reaction with oxygen and water. However the agency said it was not able to determine the exact cause of an ignition in the Helsinki City Theatre case.

Tukes issued an advisory to property owners and companies that design and maintain sprinkler systems to help prevent a similar accident.

The agency called for firms to stop using zinc-lined pipes in new sprinkler systems installed in Finland.

"The use of zinc-coated pipes in new sprinkler systems must cease in Finland. Tukes will later announce a schedule for operators in the field," it said in the statement.

Sprinkler systems already under construction can continue to use the pipes, but the agency said that contractors should be aware hydrogen may form in the systems. It noted that there might be a risk associated with emptying and modifying sprinkler pipe systems.

According to Tukes’ new guidelines, contractors must also use a hydrogen gas detector when they empty sprinkler pipes. The agency also called for firms to draw up guidelines for employees that include instructions on ventilation and monitoring pipe pressure as well as wearing protective clothing and other gear.

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