Comment

1 June 2002

Enforcing the no-fly zone

By Nicholas Sheble

The recent finding that a high percentage of knives, daggers, box cutters, mock grenades, and other metallic and dangerous objects passed through carry-on baggage screening devices and boarded planes at numerous U.S. airports was certainly unnerving.

The Federal Aviation Administration (FAA) must, according to the Aviation Security Act passed this past November, check or scan every piece of luggage that goes on an airplane, whether carry-on, checked, cargo, or mail. The FAA must be able to do this by 31 December 2002.

Many aviation experts and members of Congress assumed more X-ray machines would satisfy this mandate. Since then it has become clear manufacturers cannot produce the number of machines necessary to handle the job.

Besides, bombs don't come in particular shapes, which foils the X ray's forte. They can be round, flat like a sheet of paper, or any shape at all. They can even be found inside a can of shaving cream.

Feds focus on three

With that, the Feds are moving on and looking to the future. They have identified the commercially available sensor technologies they feel will handle some or all of the job of detecting explosives.

Higher-tech X-ray devices operate by passing X rays through screened items and projecting an image of the contents onto a monitor. The density, average atomic number, and appearance identify potentially explosive materials. The detection capabilities of these devices vary in terms of how the X-ray systems function -for example, by providing cross-sectional images or using reflected energies, or backscatter.

Some devices have an automatic alarm, while others require operators to manually signal the presence of potential explosives.

Chemical trace devices rely on identifying the presence of explosive vapors and residues associated with explosive materials. These devices are sniffers or trace detectors. Screeners obtain samples using a wipe or vacuum, or they examine a document or other item the passenger has handled. They may also sample air gathered at walk-through portals.

For each technique, a device to detect explosives analyzes the sample. Most of these devices include automatic alarming.

Electromagnetic devices use radio frequency pulses that probe baggage or other items. The pulses elicit unique responses that associate with explosive materials. These devices usually include alarming upon sensing an explosive's profile.

Sense density and atomics

The technology that is installing now is X ray related and familiar to many. The Government Accounting Office said in a report to Congress that computerized axial tomography (CAT or CT) scan is based on computer technology from the medical field that obtains a number of cross-sectional images of a bag that are displayed on a monitor.

CT is a proven, useful technology for the medical, food and beverage, biological and agricultural, construction, and other industries.

The machines provide density and effective atomic number intelligence that can match with known explosives' profiles. The device automatically alarms upon potential explosives detection.

However, it is relatively slow in processing bags. Indeed, it's also expensive, at $1 million per unit, and so heavy that some airports are redesigning their layouts so the CAT system is on the ground floor.

These drawbacks make it unlikely that CAT scans will ever be effective or feasible for screening passengers or carry-on items. As well, the reliance on imaging as part of the detection is troubling and reminiscent of the present and near-past technology that allowed the 19 hijackers aboard those three airplanes last September.

The FAA seeks a machine that says yes or no without human judgment and fallibility. That is why the FAA is looking at trace detection devices as the near-future explosives detection technology.

The Transportation Security Administration, the agency in charge of overhauling airport security, is conducting trials of lighter, smaller, more mobile trace detection machines at airports in Salt Lake City and Norfolk, Va. The units cost $40,000.

In fact, trace detection technology is already playing a bit part at airports. Highly suspect people, packages, or luggage may have already had contact with it. The FBI uses the trace detection machines to find explosives also.

But ion mobility spectroscopy (IMS) has the most immediate and near-future potential. IMS devices operate by measuring the mobility of various molecules through a gas in an electrical field. After gathering a trace sample using a wipe or a vacuum, these devices provide analysis within 5 seconds.

InTech will look more closely at these technologies in July. IT