December 2001
Popular Science
Michael Dolan
When a truck bomb went off in the basement of the Trade Center during a terrorist attack in 1993, the explosion knocked out much of the power to the building's emergency operations center, which was located beneath the ground floor. After that, the security center was relocated to a higher floor -- a sensible move, according to many engineers, who deplore the fact that the security headquarters of most office buildings are in the lobby. "You can drive a car full of explosives into the lobby, or a suicide bomber can walk in," says Klemencic. "If you lose that command center, you lose your ability to operate the building and communicate with people." That is, of course, provided that everyone can hear you. Most alarm and loudspeaker systems are connected to the emergency operations center by cables that run vertically through the building. A fire or other catastrophe can sever those cables, causing the command station to lose contact with all the floors above the area of concern.
A solution already in place in some new buildings is to equip each floor with a wireless remote fire alarm. The alarm has a sensor that provides two kinds of information to the command center: whether there is fire on the floor, and whether the sensor is in working order. Those remote signals are transmitted continuously, so any interruption should trigger an immediate response. "These devices are so sophisticated, they can even cut down on the prospects of false alarms," says Frank Carista, an electrical engineer for Turner Construction. In the event that people are unable to get out, other measures are being explored. In China, "areas of refuge" are popular with many builders. Every 15 floors or so, a floor or portion thereof is constructed of concrete slabs and designated as a place where occupants can go to wait out a fire. These areas are equipped with mechanized ventilation systems that clear the air of smoke. They are also connected to pressurized stairwells, should people need to escape a potential collapse. "The idea of building an area of refuge is particularly helpful to people who are handicapped or not in good physical condition," says James Milke, a fire protection engineer at the University of Maryland. "The prospect of walking eight floors is a lot less daunting than walking 40 or 50 floors." Moreover, high-tech systems are in the works that would enable security guards to detect a planned attack on the building before it even happens.
A device known as a laser spectrometer can sniff out explosive chemicals or poison gas within a mile of a building, depending on the wind direction. It can be placed in an innocuous-looking box about the size of a fax machine and mounted on the outside wall of a building. A pump inside the box continually sucks in gas samples from the ambient air. Those samples are fed into a chamber where they are exposed to infrared laser light. Every chemical possesses a unique fingerprint, based on the way its molecules behave on the light absorption spectrum. The spectrometer's sensors are set to recognize the specific frequencies of suspect chemicals, including the ones most commonly used in bombs. If such a frequency is detected, an alarm is tripped, alerting emergency personnel.
If a laser spectrometer had been installed at the federal building that was attacked in Oklahoma City in 1995, the device would have been capable of detecting the ammonia compounds in Timothy McVeigh's truck bomb. "We already have a device that can detect ammonia at 100 times below the odor threshold," says Patrick McCann, president and CEO of Ekips Technologies in Norman, Oklahoma. "We'll soon be able to create laser detectors that can test for a dozen chemicals or more."
Copyright 2001
Popular Science. All rights reserved.
