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How Millimeter Wave Scanners Work

        Science | Devices

The MMW Scanning Process
This monitor at the Las Vegas airport in February 2011 displays the automated target recognition software responsible for creating a generic display of a person's body. Compare that visual with the more detailed mmw image of the body on the next page.
This monitor at the Las Vegas airport in February 2011 displays the automated target recognition software responsible for creating a generic display of a person's body. Compare that visual with the more detailed mmw image of the body on the next page.
Ethan Miller/Getty Images

Millimeter wave scanners aren't metal detectors. They actually peer through clothing to look for metallic and nonmetallic objects an individual might be trying to conceal. Getting a good view requires that passengers entering the scanner follow certain procedures. Here's what you can expect if you enter one of the approximately 600 mmw scanners in use at airports across the U.S. in 2012:

  1. First, you'll need to remove everything from your pockets, as well as your belt, jewelry, lanyards and cell phone. This ensures that the scanner won't see these items and flag them as suspicious -- and saves you from enduring additional screening after you exit the machine.
  2. Next, you'll walk up a short entrance ramp and enter the imaging portal, which looks a lot like an oversized telephone booth.
  3. Standing still, you'll raise your arms, bent at the elbows, as the dual antennas rotate around your body.
  4. Then you'll exit, stage left, as a TSA agent looks at the results of your scan on a monitor attached to the machine.
  5. The TSA agent sees one of two things. If the scanner detects something suspicious, it will display a generic outline of a human figure with the suspicious item indicated by a yellow box. If the scanner finds nothing, it will display the word "OK" with no image.

Either way, the scan takes less than 10 seconds and requires nothing painful or embarrassing. But if you feel strongly that the whole-body scan of a millimeter-wave machine violates your privacy, you can opt out of the screening process. You will, however, receive alternative screening, including a physical pat-down.

According to the TSA, most people prefer the scanning process to a physical exam. In fact, more than 99 percent of passengers choose to be screened by this technology over alternative screening procedures [sources: TSA]. And people with artificial joints or other implanted medical devices appreciate mmw scanners even more because they don't have to worry about the false positives associated with old-fashioned metal detectors.