How is high-rise building evacuation different from simply leaving the building upon being notified to do so?
The multiple floors of a high-rise building create the cumulative effect of requiring great numbers of persons to travel great vertical distances on stairs in order to evacuate the building. In a typical scenario of high-rise building evacuation, it is believed that 20% of the occupants need assistance to use stairs in an emergency. In addition, firefighters will need to use at least one staircase for fire suppression and rescue operations, thereby eliminating one staircase for egress. Hence, the total evacuation in high rise is a very hazardous operation and it would take many hours to safely move all the people out of a blazing building. In the 1993 bombing of the World Trade Center, for example, we learned that in some cases it took as long as 6-8 hours for the tens of thousands of building occupants safely traversed some five million person-flights of stairs to successfully exit the buildings. The physical demands made on high-rise occupants exiting in stairwells can exceed their c
