In 1995, British Steel did a series of tests on mock structures filled with office furniture to see the stability of a steel building during different fire scenarios, to ensure that they could not collapse from high temperatures.
Footage of one of the tests, which appeared in the documentary "World Trade Center: Anatomy of the Collapse", showed an 8-story steel and concrete building full of office furniture burn for hours without structural failure.
According to the film: "This was the largest test of its kind ever conducted. It showed how unprotected steel can be distorted, even by a normal office fire. But as is typical in steel buildings, the structural beams only slowly and progressively warped and sagged. There was no chance of a sudden collapse."