Friday, December 01, 2006

A Better Liquid-Explosives Detector

The same technology used in TNT detectors in Iraq is being adapted for airport security to sniff out liquid-bomb-making materials.

By Kevin Bullis

A company based in Stillwater, OK, has developed a detector for hydrogen-peroxide explosives, which are thought to be popular with certain terrorist groups. It is now working to place its liquid-explosives-detection technology in airports.

The need for such a device was highlighted last summer, when a plot to bomb airplanes using liquid-explosives ingredients was uncovered in the United Kingdom. ICx Nomadics, whose TNT detectors are now sniffing out explosives in Iraq, has developed a device that can sense hydrogen peroxide and the peroxide-based explosive triacetonetriperoxide (commonly referred to as TATP), which was used in the subway and bus bombings in London last year. The device is sensitive enough to detect peroxide even if it is inside a factory-sealed container, says Aimee Rose, a researcher with the company.

Rose says ICx Nomadics should be ready to start tests with the Department of Homeland Security (DHS) and the Transportation Security Administration (TSA) in a couple of months. If it passes those tests, the detector, based on chemically sensitive films, would represent a novel--and potentially far faster and more accurate--way to detect liquid explosives. The company's existing TNT detectors are based on a semiconducting polymer film that was developed in the lab of Timothy Swager, a professor of chemistry at MIT. The film creates a signal when TNT vapors bind to it (see "Stopping Roadside Bombs").

The DHS is now testing 10 commercial devices for detecting liquid explosives, according to DHS spokesman Christopher Kelly. The department uses four main types of technology: X-ray, acoustic/ultrasound, Raman spectroscopic, and electromagnetic. And all of these can detect liquid explosives through a sealed container. But these devices, while sensitive, tend to return too many false positives, making them impractical for use in airports.