The experience of fires in very tall buildings contributed to the development of very tall building fire safety provisions in codes and standards. A number of fires in the recent history brought attention to the fire safety risk presented by very tall buildings. The World Trade Center attack has caused newly-focused attention on very tall buildings.
Among the significant tall building incidents are fires at the following buildings:
- One New York Plaza - August 15, 1970
- MGM Grand - November 21, 1980
- First Interstate Bank - May 4, 1988
- One Meridian Plaza – February 23, 1991
- World Trade Center Explosion and Fire – February 26, 1993
- World Trade Center Buildings 1 & 2 – September 11, 2001
- World Trade Center Building 7 (WTC 7) – September 11, 2001
- Cook County Administration Building – 2003
- Caracas Tower Fire - October 17, 2004
- Windsor Tower, Madrid, Spain – February 12, 2005
- The Beijing Mandarin Oriental Hotel Fire - February 9, 2009
While these fires were individually unique, there are common issues. These lessons have had an impact on the development of codes and standards. The general lessons learned pertain to:
- Elevator operation.
- Provision of fire restive construction.
- Combustible materials in concealed spaces.
- Protection of openings in fire rated assemblies.
- Pre-fire planning.
- Automatic sprinkler protection.
- Re-entry to floors from exit stairways.
- Maintenance of fire protection systems and egress components.
- Combustible materials on facades.
Tall buildings have attributes which can adversely affect the fire safety of a building. These features include:
- Height beyond available resources of fire department ladders. Typical fire department aerial ladders have the capability to have an effective reach (recognizing a setback distance from a building). Some building sites provide multiple levels of street access to a building. Therefore, many codes have defined “high-rise” buildings as those having an occupied floor level a defined height above the lowest level of fire department vehicle access. Buildings beyond the reach of exterior fire department ladders, then, must have additional protection features because exterior rescue and fire fighting capabilities will be limited or unavailable for portions of the building above that height.
- Extended evacuation time. The time necessary for full building evacuation increases with building height. (See the SFPE Handbook of Fire Protection Engineering and Engineering Guide to Human Behavior in Fire for more information.) In the case of very tall buildings, full building evacuation via stairways might be impractical. A “defend-in-place” strategy has been employed in many building designs by (1) designing compartments allowing people to remain in place, e.g., residential units; (2) temporarily evacuating people to areas of refuge on a floor; or, (3) moving people to dedicated refuge floors elsewhere in the building. Recently, times for full building evacuation have been reduced by employing elevators specifically designed to supplement the egress system of a building. Buildings employing assembly occupancies with large occupant loads on the upper floors of a tall building require special consideration.
- Pronounced Stack effect. Stack effect is a natural physical phenomenon which occurs in very tall buildings which experience a pressure difference throughout their height as a result of temperature differentials between outside air temperature and inside building temperatures. (See the SFPE Handbook of Fire Protection Engineering for more information.) The effect is pronounced in tall buildings because of their greater height. Stack effect causes air to move vertically, either upward or downward in a building. It can cause smoke from a fire to spread in the building if it is not controlled. As a result, tall buildings include features such as automatic sprinkler protection to limit the size of fires and the resulting quantity and energy of smoke which can spread throughout the building, and smoke control means such as openable panels and mechanical systems to either vent, exhaust or limit the spread of smoke throughout the building.
- Water supply limitations. The water supply needs in tall buildings can be beyond water supply capability of public mains and fire department pumpers. Public water supplies have pressures which will require supplemental pumps in the building to boost the pressure to a usable level on the upper floors of a building. The building’s fire department connection allows the fire department to supply water to the sprinkler and standpipe systems in the event the building’s water supply is out of service or inadequate. Above the height achievable by the local fire authority pumps, buildings must have the capability to supply its water independent of the fire department appliances. Therefore, multiple levels of pumps and water storage tanks are provided. Also, because of this potential loss of an external water supply, additional protection features may be considered necessary for such buildings.