Some people also put important documents, photos and other valuables in a fireproof safe, just in case.

The failure occurred due to faulty repair of the bulkhead, when a double row of rivets was replaced by a much weaker single row.

It was slow going, but hopes remained high until September 18, when a canary inserted beyond a bulkhead by oxygen tank equipped workers died.

Gage, who is a member of the American Institute of Architects, has worked as an architect for 20 years and was involved in the construction of numerous fireproof steel frame buildings.