WASHINGTON — A system that detects the faint electric signals of beating human hearts is being used to help rescuers frantically seeking to locate people trapped under the rubble in China's horrific earthquake.
That's just the latest use for a decades-old technology that's been put to use by the military, law enforcement, and first responders to find people who've survived train wrecks, avalanches, explosions or other accident scenes.
One product called LifeGuard, made by DKL International in Vienna, Va., has detected at least 17 victims from the China quake, which struck May 12 in Sichuan Province.
The device also was used to pick up the heartbeat of a victim of the 2001 World Trade Center collapse, though that rescue effort failed. The Japanese police ordered 100 DKL detectors in 2004 because their nation is so vulnerable to earthquakes.
Another company, Geovox Security Inc., of Houston, has sold 150 of its AVIAN Heartbeat Detectors for use in immigration, border control and prison agencies around the world. Geovox claims its system can detect a concealed passenger in less than a minute, allowing rapid vehicle searches without disturbing the contents.
Theoretically, heartbeat monitors could spot illegal immigrants crammed in the back of a trailer truck crossing the Mexican border. A prisoner trying to escape by hiding in a laundry truck could be caught by a detector developed at the Energy Department's Oak Ridge National Laboratory in Tennessee. A terrorist could be intercepted stowing away on a ship or sneaking into a nuclear power plant.
Volvo even offers a device to let you check for an intruder lurking in the back seat of your car before you open the door.
Various heartbeat detection devices have been invented over the last 40 years. Some use electrical signals, others infrared radiation or ground-penetrating radar. Some proved unable to distinguish a genuine pulse from surrounding noise, or to detect faint signals through concrete or metal walls.
The DKL LifeGuard system in use in China works like the familiar electrocardiogram (ECG) that cardiologists employ to monitor the electrical field created by a beating heart. The heart's activity generates a low-frequency electric field that penetrates the skin and extends in a circle around the body.
The company says its handheld device, which costs $12,000 each, can pick up signals 20 to 50 meters away through a one-meter thick concrete wall, heavy foliage and rocks, and pinpoint the person's location accurately. It can track an individual standing in the open at a distance of 500 meters.
In contrast, the Geovox system doesn't detect electrical signals, but rather senses tiny shock waves created by a beating heart of a person who is touching a solid object, such as the side of a truck. The Department of Homeland Security has issued a contract to Geovox to upgrade its system, which can be fooled by winds or other activity.
(Editors note: Nancy Walcott, DKL's public affairs officer, is married to John Walcott, the chief of McClatchy's Washington Bureau.)
ON THE WEB
See a video of a Chinese rescue worker using a handheld heartbeat detector.