Jeffrey Heller of Heller Manus Architects spoke at a meeting of the San Francisco Planning and Urban Research Association. Because very large buildings, such New York City's World Trade Center, are prime targets for terrorism and attacks because of both physical size and cultural status, "in the United States, nothing like this is going to happen in the next decade," says Heller. "People won't want to be on the upper floors. The insurers won't insure it."

Heller, the head of the local chapter of the American Institute for Architects, is part of a professional team working to make safety improvements within large structures, including the World Trade Center. His focus is on making emergency entries and exits safer for rescue workers and occupants. The team is currently working on the concept of an impact resistant shell encasing the service elevator shaft, service lobby and stairway, creating "an area of refuge" in the event of an emergency.

According to Heller, a change like this could become part of an international working standard for high-rise buildings, as it is a logical solution that is not a huge burden to the overall building design.