U.S. Airport Full Body Scanners Too Unreliable to Use, Germany Says Interior Minister says scanners sometimes mistake underarm sweat for bombs.

Sept. 1, 2011  -- The German government halted the full roll out of American body imaging scanners in the nation's airports today after the Interior Minister said the devices sound too many false alarms -- including at times mistaking underarm sweat for dangerous chemicals.

The determination came after a months-long test of a pair of L-3 Communications ProVision ATD human imaging scanners -- the same type of scanners already in use in dozens of airports across the U.S.

Over 800,000 Germans voluntarily tested the scanners at an airport in Hamburg from September 2010 to July 2011, during which time airport security reported so many "unnecessary alarms" that Interior Minister Hans-Peter Friedrich said the technology, "despite the high detection performance," has not yet matured and is "not yet suitable" for general practical use. Local press reports put the false alarm rate high as 49 percent and said sweaty armpits had been the culprit multiple times.

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The German decision comes just a day after a 9/11 anniversary report by the Bipartisan Policy Center said U.S. was still "highly vulnerable to aviation security threats," partially because it said full body imaging for explosive detection is unreliable.

"With significant federal funding, the [Transportation Security Administration] has deployed large numbers of enhanced screening equipment used at passenger checkpoints and baggage check screening. Unfortunately, explosives detection technology lacks reliability and lags in its capability to automatically identify concealed weapons and explosives," the report says.

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A TSA official told ABC News the administration could not comment on another country's technology and testing methods, but said the ProVision system is customizable and it is not known if the Germans were using the exact same models, standards and calibrations that U.S. airports use with their scanners.

"As with any technology, false alarms remain a possibility," the official said. "But this is the best available technology as one of our many layers of security to provide the best opportunity to detect dangerous items, such as explosives."

Approximately 250 ProVision scanners are in use in the U.S. currently, according to the TSA, from Atlanta to San Francisco to Honolulu. The TSA is in the process of upgrading all of those systems to the newer ProVision ATD model.

The ProVision scanner, which uses "safe active millimeter wave radio frequency," is one of two options from which American airports can choose for full body imaging. The other system, known as "backscatter," uses X-ray technology to scan passengers and is used in machines built by L-3 Communications' competitor Rapiscan.

The TSA credits both technologies with catching 300 "dangerous or illegal weapons" since January 2010 alone.

"Our top priority is the safety of the traveling public, and TSA constantly strives to explore and implement new technologies that enhance security and strengthen privacy protections for the traveling public," TSA Administrator John Pistole said in July when announcing the upgrade to the ProVision systems.

In addition to concerns over reliability, full body scanners have come under significant scrutiny for potential privacy violations. The ProVision "image-free" upgrade, for instance, replaces the 3-D black and white silhouette of the passenger with a "generic, computer-generated outline of a person," according to the TSA.

After the failed December 2009 shoe bombing plot, the TSA worked closely with foreign governments to promote the use of advanced imaging technology (AIT), according to a report by the Government Accountability Office.

L-3 Communications declined to comment for this report. Rapiscan Executive Vice President Peter Kant said the company "clearly disagrees" with the 9/11 Commissions findings on full body scans and said multiple independent and government tests have found the Rapiscan technology more reliable than any other passenger inspection method.

ABC News' Clark Bentson and Troy Mullen contributed to this report.

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