Occupants and Safety Systems

On any given workday, up to 50,000 office workers occupied the World Trade Center, and 40,000 people passed through the complex.

The World Trade Center contained the offices of 430 businesses from 26 different countries.

Doors leading to the roof were locked. There was no rooftop evacuation plan. The roofs of both the North Tower and the South Tower were sloped and cluttered surfaces with radiation hazards, making them impractical for helicopter landings and as staging areas for civilians. Although the South Tower roof had a helipad, it did not meet 1994 Federal Aviation Administration guidelines.

To manage fire emergency preparedness and operations, the Port Authority created the dedicated position of fire safety director. The director supervised a team of deputy fire safety directors, one of whom was on duty at the fire command station in the lobby of each tower at all times.

Deputy fire safety directors conducted fire drills at least twice a year, with advance notice to tenants. "Fire safety teams" were selected from among civilian employees on each floor and consisted of a fire warden, deputy fire wardens, and searchers.

Most civilians recall simply being taught to await the instructions that would be provided at the time of an emergency. Civilians were not informed that rooftop evacuations were not part of the evacuation plan, or that doors to the roof were kept locked.

The Port Authority acknowledges that it had no protocol for rescuing people trapped above a fire in the towers.

The World Trade Center lacked any plan for evacuation of civilians on upper floors in the event that all stairwells were impassable below.

Between 16,400 and 18,800 civilians were in the World Trade Center complex at 8:46 a.m. on Sept. 11, 2001.

Approximately 87 percent of the estimated 17,400 occupants of the towers, and 99 percent of those located below the impact floors, evacuated successfully.

A principal factor limiting the loss of life was that the buildings were one-third to one-half occupied at the time of the attacks. The National Institute of Standards and Technology (NIST) estimated that if the towers had been fully occupied with 20,000 occupants each, it would have taken just over three hours to evacuate the buildings and about 14,000 people might have perished because the stairwell capacity would not have been sufficient to evacuate that many people in the available time.

Sources: Final Report of the National Commission on Terrorist Attacks on the United States (July 22, 2004); National Institute of Standards and Technology, Final Report on the Collapse of the World Trade Center Towers (September 2005), September 11 News (Web site); World Trade Center Facts (Web site)