Housed as it is on the Otago harbour waterfront, the Forsyth
Barr Stadium's roof may seem threatened more by winds,
flurries of snow and the odd hail storm than by the ravages
of fire.
But the safety of the ethylene tetrafluoroethylene (ETFE)
covering in the event of a fire has continued to exercise the
minds of the project's opponents.
The debate reared its head most recently on the Otago Daily
Times' website comments section, a site where readers get the
chance to respond to stories.
The story in question told of Dunedin City Council chief
executive Jim Harland's return to Dunedin with offcuts of the
material, after a recent visit to the Beijing factory where
it was being joined.
The ETFE was manufactured by Vector Foiltec in Singapore and
Germany, before being shipped to the factory in Beijing and
welded into 1.5m by 5m pillows secured against sections of
rope, Mr Harland said at the time.
One respondent asked "how flame-resistant is ethylene
tetrafluoroethylene?".
"Can it withstand fireworks or flares?"
Another said information he had found showed "ETFE can burn,
produces highly toxic gases when it decomposes from heat or
burning, and in a fire, molten ETFE can stick to skin causing
burns".
To get to the bottom of how ETFE responds in a fire, the
newspaper - literally - applied the blowtorch to ETFE.
Samples of the material were taken to the Dunedin Central
Fire Station, and under the supervision of Deputy Chief Fire
Officer Trevor Tilyard, burned.
What was instantly noticeable was that the material refused
to burn unless a flame was being held directly to it.
The material disintegrated when the flame was applied, but
immediately stopped burning when the flame was removed.
Vector Foiltec advertises the material as "self
extinguishing", and says drops of molten ETFE will not burn.
That appeared to be the case.
One piece dropped away from the main sheet being burned, but
was not alight when it hit the ground about a metre below,
and could be picked up straight away.
"I think that's performing very well," Mr Tilyard said.
On the question of fireworks or flares, Carisbrook Stadium
Trust chief executive Malcolm Farry said they would not be
used at the new stadium.
"We won't be setting off fireworks," he said.
Instead, laser light shows, which had been used "to huge
effect" at events worldwide would be used.
"They are the next generation beyond fireworks," he said.
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