A Better Baggage Scanner?

How safe is commercial air travel after Sept. 11, 2001? The answer is still up in the air.

While U.S. federal agencies and the transportation industries have undoubtedly made some strides, it's often been with mixed results.

Consider, for example, the safety of airline baggage. The federal government moved swiftly to install baggage screening machines in all of the nation's 429 commercial airports so every piece of luggage could be scanned for explosives before being loaded onto a commercial jet.

However, according to a recent report by the Transportation Department, some of the machines produce a high-rate of "false-positives," or indications of explosives when there aren't any.

The problem, say experts, is that current baggage screening systems produce monochromatic X-ray pictures that cannot distinguish between a block of plastic explosives or a wedge of cheese.

"These machines are highly reliant on the operator," says Johnathan Tal, president of Homeland Security Research Corp., in San Jose, Calif. "We spent $2 billion on these machines and God knows how many billions to deploy them by the end of last year and we have probably a 30 percent error rate."

Tell-Tale Nuclear Signatures

Several companies believe that the answer to better luggage screening may soon come from refinements in a decades-old technology known as neutron activation.

Such neutron scanners work straightforwardly enough. The machine bombards an item — a piece of luggage or even a truck-sized shipping container — with a burst of high-energy neutron particles.

When the particles encounter various elements such as carbon, nitrogen, chlorine, oxygen and iron, specific patterns of gamma radiation are reflected off the object. Detectors pick up these "backscattered" radiation patterns and send them to a computer that analyzes them against known, unique "signatures" of explosives, drugs, and chemical or biological warfare agents.

Good Enough for the Military?