That is how long it would take from the moment a significant fire started for thick and toxic smoke to rise to the ceiling, billow back down and overwhelm those seated in the building's highest seats.
It is a threat that has been exercising the minds of Dunedin City Council staff, their consultants and New Zealand Fire Service authorities while planning the $45.8 million upgrade of the Town Hall, Municipal Chambers and Glenroy Auditorium-Dunedin Centre.
A decision to issue building consent for the project is imminent, and an announcement on the contract to carry out the work is expected within two weeks.
Council chief building control officer Neil McLeod emphasised the consents would not be granted until every detail was checked and approved.
A significant portion of the overall spend was on fire safety improvements to get patrons out quickly and safely, and to protect surrounding buildings, while allowing emergency services in, Mr McLeod said.
"The fire performance of the building is always mission-critical.
It's obviously one of the things that has the potential to be disastrous if you get it wrong."
His comments came as the Otago Daily Times was yesterday shown building consent documentation, including a Fire Service report on the safety of the building's design.
The May 17 report mixed praise for "significant" fire safety improvements with concern over inadequate information about what was planned.
The upgrade would include new automatic fire sprinklers, smoke detectors and an upgraded mechanical smoke extraction system, as well as emergency lighting, signs and fire partitions.
The Fire Service report noted concern about the "tenability" of the gods, the highest seated area at the back of the Town Hall, in a fire.
Information from the council suggested patrons would have 300 seconds to evacuate, but Fire Service modelling suggested the time could be "as little as 130 seconds".
That would be "well before" patrons could reasonably be expected to escape the area in a fire, it warned.
Council building control officer Mark McLay said concerns raised by the Fire Service had resulted in a peer review of fire safety procedures, which clarified patrons would have 290 seconds to escape.
Extra emergency floor lighting would also be installed to guide patrons to the nearest exits quickly, he said.
The Fire Service was satisfied, and the changes had been signed off this week, he said.
Mr McLeod said the wording of the Fire Service report was "not uncommon", but the issues needed to be addressed.
The gods could be a "scary place" from a fire safety perspective, but would be "significantly less scary" as a result of the upgrade, he believed.
"This is a high-class upgrade to that building.
"I won't say no expense is being spared, but it's not a low-level upgrade."
The upgrade comes 80 years after the Town Hall opened its doors to the public on February 15, 1930.
The project would also include replacing the existing entrance with a glass cube, and a general upgrade of seating, lighting and theatre services, the surrounding foyer areas and other facilities.
More than $20 million of the total cost was being spent on fire safety and other regulatory upgrades across all parts of the building.
Town Hall plans
- Building consent imminent, contract to be announced within two weeks.
- $45.8 million project to begin within weeks of contract being awarded; completed by December 2012.
- Municipal Chambers refurbishment starts first; completed by March next year.
- Glenroy Auditorium-Dunedin Centre upgrade starts April-May next year; completed by December 2012.
- Town Hall upgrade initial work starts April-May next year; in full swing by October; completed December 2012.
