Patting down for PETN
Image by Getty Images via @daylifeNew airport security procedures that have stirred the emotions of air travelers — full-body scans and aggressive pat-downs — were largely designed to detect an explosive powder called PETN, which has been a staple of Al Qaeda bomb makers for nearly a decade.I think many of those complaining about the new screening procedures are forgetting about the threat posed by PETN bombs that are difficult to detect using less invasive means. As I have said before, I have been through the machines and the pat downs and did not think either was any big deal.
It was PETN that was molded into the sole of Richard Reid's black high-top sneaker when he walked onto American Airlines Flight 63 bound for Miami in December 2001.
It was PETN that was sewn into the underwear of Umar Farouk Abdulmutallab, authorities say, when he boarded Northwest Airlines Flight 253 for Detroit on Christmas Day 2009.
And it was PETN that suspected Al Qaeda operatives in Yemen packed inside computer printer cartridges that were shipped Oct. 28, intending to blow up planes en route to Chicago.
None of the plots succeeded in taking down an aircraft, but top U.S. officials are concerned about fresh indications that Al Qaeda remains determined to get PETN on airplanes by trying to exploit vulnerabilities in passenger and cargo screening.
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PETN, or pentaerythritol tetranitrate, presents some vexing problems for security experts. A powder about the consistency of fine popcorn salt, it will not trigger an alarm on a metal detector. Because of its more stable molecules, PETN gives off less vapor, making it more difficult to detect by bomb-sniffing dogs and the trace swabs used by the Transportation Security Administration.
PETN's stability makes it easy to hide and easily transformed. When mixed with rubber cement or putty, it becomes a rudimentary plastic explosive — a baseball-sized amount can blow a hole in an airplane fuselage.
"PETN is hard to detect and lends itself to being concealed," said an intelligence official who was not authorized to speak on the record. "It packs a punch."
One way to detect PETN is through its detonator, which typically uses materials that are easier to trace. Reid's shoe bomb combined PETN with a volatile explosive accelerant called TATP that can be made from dime-store nail polish and hydrogen peroxide. The Yemen printer cartridge bombs placed the PETN around small homemade blasting caps containing the chemical lead azide.
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The new aggressive pat-downs and the increased use of full-body scanners — there are more than 400 machines in 69 U.S. airports — were a direct response to last year's alleged bombing attempt on Christmas Day, when Abdulmutallab passed through screening with 80 grams of PETN, authorities say.
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While I am 66 years old and do not fit the profile of a bomber, I do not mind the screening. I do always look at the other passengers to see if there are any who do fit the profile and them examine them closely from a distance. One of the things I did notice, even flying through the Middle East is how few passengers actually fit the terrorist profile.
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