Buildings may be more prone to fire damage than believed

Fireproofing like type used in WTC towers questioned in U.S. study


NEW YORK - Hundreds of buildings nationwide with fireproofing similar to that used in the World Trade Center could be far more prone to structural damage during major fires than previously thought, according to a preliminary calculation by federal investigators.

The investigators are studying the precise causes of the World Trade Center collapse.

Their work includes calculations of how heat moves through steel building components with small gaps or imperfections in fireproofing insulation.

Their inquiry, which is in its early stages, shows that during a fire such flaws can act as sluice gates for heat, allowing it to enter the steel, where it becomes trapped, weakening the structure.

Countless buildings put up since the 1960s have used the same type of lightweight, fluffy, spray-on fireproofing to protect their steel.

Photographic evidence of the trade center suggests that this material, which is easily damaged, had gaps and possibly larger missing sections.

Experts say similar problems are also found in ordinary high-rises.

The investigators want to examine the fireproofing in New York City buildings of similar vintage, and the city's Buildings Department has agreed to help identify them.

Patricia J. Lancaster, the buildings commissioner, said that the use of spray-on fireproofing was extremely widespread in the city.

"It's everywhere," Lancaster said. "It's easy to apply, and it's light."

She said that because many fireproofing subcontractors do excellent work, she would be surprised if large variations in thickness, like gaps in the insulation, turned up in every building that was inspected.

But, she added, not enough attention has been paid to concerns such as the long-term durability of patches to fireproofing.

Patches are applied after parts of the coatings are removed during work on ducts, wiring or sprinklers.

Investigators said their findings could have implications beyond the collapse of the towers.

"When we entered into this investigation, there clearly was a concern with explaining why buildings that looked like they would stand forever came down," said Richard G. Gann, a senior research scientist at the Building and Fire Research Laboratory of the Commerce Department's National Institute of Standards and Technology in Gaithersburg.

That is where this $16 million investigation into the sequence of structural failures that led to the collapse of the World Trade Center - buildings that looked as if they would stand forever - is being conducted.

But, Gann said, "there are implications for other buildings, even if they are of different construction types, different styles, even conventional buildings."

S. Shyam Sunder, the leader of the investigation, warned that it was too soon to know if a formal bulletin or alert would be issued.

He pointed out that no large-scale survey of fireproofing in high-rise buildings has been done, and that even with variations, it could turn out that in some cases fireproofing thicknesses are conservative or sufficient for protection in all but the thinnest spots.

He said investigators have looked at only a small number of buildings in the Washington area, near their laboratories.

In those buildings, they found substantial variations in fireproofing thickness.

He said they hoped that the inspections of the New York City buildings would yield closer parallels with the World Trade Center.

Whatever the variations in the thickness of the fireproofing in the New York buildings turn out to be, he said, the team's calculations have focused only on individual steel components rather than on the overall building structure.

"We need to understand what the effect of this is on the performance of the components as a whole," Sunder said. "As we complete the work and can make definitive findings on fireproofing variability, then a recommendation can be made."

But other researchers are saying that the implications for ordinary buildings could be the most important outcome of the inquiry.

"When the investigation is over, this issue will radiate out to other buildings that have fireproofing in them," said Glenn P. Corbett, a member of the investigation's advisory committee and an assistant professor of fire science at the John Jay College of Criminal Justice. "We really have to decide whether it's appropriate to continue to use this type of material."

Whether the collapse of the twin towers was inevitable given the structural damage done by the hijacked planes or whether the towers would have been able to stand with better fire protection is not known.

The exact sequence of failures that led to the collapse has not been determined.

The federal investigation will try to answer these questions before a final report is released next fall.

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