Smith installs IMS EDS at three additional airports

Published 14 January 2006

Innovative EDS company installs IMS-based detectors in more of the country’s airports

Let us reiterate: Explosive detection is big business, and it is getting bigger. Pine Brook, New Jersey-based Smiths Detection, a provider of trace detection and X-ray security screening equipment, had its Sentinel II explosive detection walk-through trace portal deployed at the Charlotte-Douglas International Airport (CLT). The Sentinel II was deployed earlier this week at two Washington, D.C. metro area airports, Reagan National (DCA) and Washington Dulles International (IAD). The Sentinel is already deployed at two major New York City airports, Newark Liberty International and JFK International.

The Sentinel II enhances explosive detection capabilities by rapidly detecting various explosive substances that could emanate from a passenger’s clothing, skin, or hair. This non-invasive walk-through scanner reduces the need for pat down procedures at airport checkpoints.

Using Ion Mobility Spectrometry (IMS), the walk-through trace portal operates automatically, passing air gently over a person from head to toe, releasing any particles that are naturally absorbed by or cling to a person’s clothing or body. These particles are then drawn by a vacuum and collected for analysis at the passenger’s feet. Detection of particles or vapors can indicate that a person is either carrying an explosive device or has come into contact with explosive substances.

-read product specs at company Web site

Ion Mobility Spectrometry: How does it work

X-ray scanners and metal detectors may alert airport security to the presence of hidden metal weapons, but they cannot pick up on organic-chemical hazards such as explosives, biological warfare agents, toxic industrial chemicals, and illegal drugs. To detect traces of chemicals which evaporate from the surfaces of these substances, security officers now employ different kinds of chemical sniffers, and ion mobility spectrometers (IMS) are among the more popular.

IMS technique separates and detects electrically charged particles (ions) which have been sorted according to how fast they travel through an electrical field in a tube. Small ions travel very fast so they reach the detector first, as successively larger and slower ions follow along behind. A passenger walks through an IMS portal, and a gentle breeze dislodges particles from his or her clothing and skin. The particles flow into a small heated chamber. Inside the chamber, traces of the organic compounds picked off the passenger evaporate and mix with a carrier gas which is swept into the main part of the instrument. Inside the instrument, a radioactive substance, typically 63Ni, is housed in a small chamber which is shielded from the outside but is accessible to the inside of the instrument. This radioactive source constantly gives off high-energy electrons, which collide with the sample molecules and the carrier gas to form ions. Unlike the mass spectrometry technique, which relies on very low pressures to keep the ions from colliding with each other, IMS operates at normal atmospheric pressure and the ions collide with each other over and over again.

The ionized gas moves through an electrical field inside a drift tube. Smaller ions collide less frequently than large ions because they present a smaller target and are harder to hit. Thus, they move through the tube relatively unimpeded and reach the detector first. The largest ions take several seconds longer to travel to the detector because they collide more frequently with other ions along the way and are slowed down.

IMS technique has advantages and disadvantages over competing detection methods. The disadvantage: IMS sorts molecules only by size, not by chemical properties or other identifying features. As a result, it is not an especially good technique for making positive identification of unknown compounds. The advantage: IMS can make a measurement in only a few seconds, compared with several minutes to over an hour for more conventional techniques such as chromatography and mass spectrometry.

-read more in Nancy McGuire’s “Chemistry 101: Ion Mobility Spectometry,” Chemistry, 9 August 2004