Powdery PETN Poses Screening Challenges

The Transportation Security Administration (TSA) enacted Monday enhanced security measures for US and international airlines flying to the United States particularly from "state sponsors of terrorism or other countries of interest."

"Because effective aviation security must begin beyond our borders, and as a result of extraordinary cooperation from our global aviation partners, TSA is mandating that every individual flying into the United States from anywhere in the world traveling from or through nations that are state sponsors of terrorism or other countries of interest will be required to go through enhanced screening," TSA announced Sunday.

State sponsors of terrorism include Cuba, Iran, Sudan and Syria, according to the US State Department, while countries of interest include Afghanistan, Algeria, Iraq, Lebanon, Libya, Nigeria, Pakistan, Saudi Arabia, Somalia and Yemen.

The enhanced screening comes in the wake of the attempted Christmas Day bombing of Northwest Flight 253 allegedly by Umar Farouk Abdulmutallab, who traveled from Nigeria to Detroit, Mich., which an explosive concealed in his underwear.

Jimmie Oxley, a researcher at the Department of Homeland Security (DHS) Center of Excellence for Explosives Detection, Mitigation and Response (ALERT) at the University of Rhode Island, isn’t surprised by the changes occurring in screening procedures.

Changes in screening also occurred after "shoe bomber" Richard Reid attempted to blow up an airliner with pentaerythritol tetranitrate (PETN), the same substance used by "underwear bomber" Abdulmutallab, Oxley told Homeland Security Today.

"PETN is a secondary explosive so it usually requires a detonator to go off. He didn’t have a detonator, presumably because they are pretty straightforward to detect," Oxley explained.

"The shoe bomber, Richard Reid, had a primary explosive in his shoe. Primary explosives are sensitive to mild stimuli, such as impact in flight," Oxley added. "Security has changed since then. Now we all take off our shoes."

As Abdulmutallab could not have smuggled a detonator through security as Reid did, he apparently attempted to rely on a chemical reaction to generate enough heat to initiate an explosion with PETN–which is notan easy task.

Oxley predicted a more strict set of screening standards for people would eventually result from the bombing attempt on Flight 253. TSA already has technology that could detect PETN, which is a light powdery substance in the same family of chemicals as nitrocellulose and nitroglycerin.

"You’re talking about an explosive on his person," she said. "We have a fairly rigorous set of protocols for materials in checked baggage, responding to Pan Am 103. We also have a fairly rigid set of protocols for carry-ons. But we haven’t worked too much on what is carried on a person. Certainly millimeter wave and the puffers already in some airports are some ways to go about that."

Oxley cautioned, however, that liquid explosives detectors sought by TSA after the plot to blow up US-bound airliners from London in August 2006 would not necessarily have been useful in stopping Abdulmutallab’s alleged smuggling of PETN.

"There’s no reason to think that the liquid he was trying to inject it with was even an explosive. It was something that was trying to initiate a reaction. He was trying to generate enough heat to set off an explosion. So even if you had a liquid explosive detector that might not have helped in this particular case," she remarked.

PETN itself could prove challenging to detect without full body imaging through the millimeter wave or backscatter x-ray technology, Oxley said. PETN, as a light powder, is very similar to many illicit drugs, which drug dealers have continued to smuggle into the United States despite many attempts to interdict them.

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