A sniffer on the machines is held an inch from a container to draw in vapors. An attached sensor displays the level of explosive material in the vapors and can detect explosives in glass, plastic and metal containers. The TSA plans to acquire 282 bottle scanners this year.
Bottle-scanning has been a priority since August 2006, when authorities disrupted an alleged plot to blow up U.S.-bound airplanes using liquid bombs. A subsequent policy that lets passengers carry only a half-dozen or so 3-ounce bottles through security is likely to remain in place for the near future.
*Status: Limited deployment.
One technology that has fallen short of expectations is trace portals, commonly known as "puffers." They shoot jets of air at passengers to dislodge explosives particles from clothing and skin. The portals, slightly larger than a phone booth, have built-in sensors to detect explosives residue.
The TSA had planned to install 434 of the machines, but the puffers have faced problems detecting explosives and from breaking down, according to a report this year by Congress' Government Accountability Office.
Only 95 machines have been installed at airport checkpoints. The TSA, which is working with manufacturers on improvements, has no plans to acquire more.
*Status: Sidelined for improvements.
Another checkpoint inconvenience -- shoe removal -- is likely to stay in place. Hawley last summer declared "not ready for prime time" a shoe-scanning device that was thought to hold imminent promise for use at checkpoints around the USA.
The ShoeScanner by General Electric subsidiary GE Security began operating with much fanfare in January at Orlando International.
Verified Identity Pass, a contractor the airport hired to run expedited security checkpoints for fee-paying passengers, installed the machine. Verified has installed ShoeScanners at airports in San Francisco, New York's Kennedy, Newark, Indianapolis, Cincinnati, Little Rock and San Jose, Calif. But the TSA won't allow the machines to be turned on because it says they are not good enough at finding shoe bombs or other weapons.
The machine is operating only in Orlando, where the TSA has added security measures to compensate for the ShoeScanners' deficiencies. An upgraded version of the ShoeScanner is being tested in a Homeland Security Department lab.