The National Institute of Standards and Technology, which is investigating the cause of the buildings' collapse on Sept. 11, 2001, recreated the World Trade Center fire in a mock cubicle.
Investigators discovered that while the jet fuel and the plane's contents burned up in a matter of minutes, the contents of the buildings, including the many office cubicles on the upper floors, continued burning until the structures collapsed.
NIST, a part of the Commerce Department, is conducting a two-year inquiry to create a computer model of the tragedy. The goal is to understand exactly how the fire evolved in the towers, and the specific factors that contributed to their collapse.
``What we are ultimately trying to model is the spread of a fire through the building,'' said Shyam Sunder, lead investigator for the NIST investigation.
Sunder showed a video of the fire test to a group of advisers on Tuesday, the first of a two-day meeting to discuss the status of the investigation.
The World Trade Center fires have to be compared with previous tests for office fires done in decades past so NIST can suggest revisions to fire and building codes, Sunder said.
Building and fire codes in many cities are based on tests conducted on older types of offices, where computers and similar technology were less common, he said.
NIST's mock cubicle was patterned after the offices of Marsh & McLennan Cos. Inc., a consulting and risk management company which leased eight floors near the top of Tower One. They lost 295 employees and consultants.
The tests showed the fire consumed more than 300 pounds of matter in a single cubicle in just a half hour. Fire experts recreated a cubicle with a computer, a desk full of books and papers, and videotaped the fire spreading through the cubicle from a nearby heat source.
A key remaining question, Sunder said, is ``whether the suspension ceiling was intact or whether it fell'' from the impact of the plane. If the ceilings fell, they would have had a dampening effect on the spread of the fire through offices.
Researchers at the University of Buffalo are currently conducting tests to determine how much shaking those ceilings could have taken before falling.
Investigators also plan to begin next month a program of interviewing survivors of the attacks, in order to better understand the evacuation process, and be able to make improvements in things like stairwell size and evacuation patterns.
NIST is also examining the fireproofing between floor supports, the steel exoskeleton that held up the building, and emergency personnel response to the disaster.
