Following are excerpts from an article in
Fire Engineering.
"The terrorist attack on the World Trade Center (WTC) on September 11, 2001, resulted in the loss of 2,819 lives. ... In their efforts to save civilian lives at risk in the Trade Center, 343 firefighters and many other emergency personnel died. It was a 90-minute operation that ended in catastrophe. ...
"The elevators in the buildings contained recall and firefighter service features ... On 9-11, elevators in the North Tower were ... nonoperational because the recall feature was not working—they were not returning to the lobby for firefighter use. ...
"Public address speakers ... were used in the South Tower immediately following the first plane crash into the North Tower to direct occupants to remain in their offices and not evacuate."
Fortunately, common sense prevailed in the South Tower (if not at the Port Authority), and
"Most people in the South Tower began evacuating the building as soon as the North Tower was hit, ignoring taped Port Authority messages broadcast over the building's intercom system to stay where they were ... "
"So many factors combined to result in the 343 firefighter deaths on 9-11. The most fundamental and prominent are readily apparent.
•The breathtakingly high towers were able to sustain the impact of a 767 jet plane but not the ensuing fires, denying firefighters that critical period of time needed to save all of the savable.
•The radio system, under the prevailing conditions, made critical fire department communications difficult to impossible. Vital messages and orders were lost or went unheard.
•Elevators were unusable for fire department operations in both towers, removing a critical—and swift—means of access and egress.
•Interagency communications and a coordinated, interagency command structure were practically absent at a time when they were most needed."
Read more:
http://www.fireengineering.com/articles/print/volume-155/issue-9/world-trade-center-disaster/volume-i-initial-response/world-trade-center-disaster-initial-response.html