Unconventional-weapons threat

Experts suggest placing the main emergency-ops center on the ground floor, in a fortified room linked to fire-safe stairs. At least one other command center should be located off-site, in case the main one is destroyed. Freedom Tower designers are not revealing the centers´ locations.

THE CYBERBUILDING
Someday, sensors embedded in walls, floors, elevator shafts, ventilation and mechanical systems-even in bricks, steel and concrete-will take the pulse of a building, monitoring everything from temperature to structural integrity and streaming that information to the command center. Sensor data could also be invaluable to emergency workers. The Sensor-Driven Fire Model, a prototype being developed by the National Institute of Standards and Technology, uses signals from embedded heat, smoke and gas sensors to predict the size and growth pattern of a fire and streams that information to firefighters so they can anticipate conditions and the projected path of the blaze. Other sensors in floors, doors and stairways could relay the location of trapped occupants.

AIR FOR OCCUPANTS
In a skyscraper with a traditional ventilation system, an airborne agent released in a single location could infect the entire building in about 20 minutes. The solution: small, independent heating, ventilation and air-conditioning systems. The Freedom Tower is to have two such units on every floor. In an emergency they will take in air rather than blowing it out, to contain the threat.

AIR FOR RESCUERS
Firefighters carry 70 pounds of gear, and they feel it when hiking up hundreds of stairs. Then 30 minutes later they have to head down to refill their tanks. Not in the plans: The Rescue Air System, a pipe that runs vertically through a building, provides stations where responders can get compressed air.

WATER WORKS
The Freedom Tower will have two sprinkler systems operating on each floor, both housed within concrete structures for fire protection. Not in the plans: Security experts laud such redundancy but suggest an added layer of defense: self-contained water-mist units-sprinklers that release an intense fog of water droplets. Because these units require minimal water, they can be fitted with their own tanks, to ensure that the failure of one system won´t affect the others.