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Reliably Detecting Explosives

THE ABILITY TO detect explosives in the field remains a challenge, but the National Institute of Standards and Technology (NIST) has multiple teams working on one piece of the puzzle—facilitating standards and uniformity of results.

Many federal agencies and first responders use canines to seek out explosives. NIST is tasked with creating vapor-based training aids for the dogs. Bill MacCrehan, a NIST research chemist, tells Security Management that the Metrology and Standards for Canine Olfactory Detection of Explosives Group has developed a technology that captures and releases the odors associated with explosives. With this technology, trainers don’t need to use actual explosives when training the dogs.

There are no mandated regulations on how explosives-detecting canines are trained. A number of public and private trainers have different training methods, so one canine’s trained snout varies widely from another’s. Another issue is that “not all samples give off the same amount of odor,” MacCrehan explains. “One sample of a C4 explosive could give off 10 times as much [odor] as another sample in our testing. When a trainer says their dog is trained to detect C4, which [sample] is it? One is 10 times stronger than the other.”

MacCrehan’s team works on identifying which compounds in an explosive the dogs can actually smell. They isolate the vapors of those compounds and apply them to training aids. Another important task of the team is to develop a method for containing and releasing the vapors. MacCrehan says there are some commercial training aids on the market, but they don’t account for how the passage of time might affect the scent. NIST, on the other hand, is working to develop a method that will keep the vapor’s composition constant over time.

MacCrehan says it’s important to use vapors in training because they have the same compounds as the actual explosive. Using live explosives in training is expensive, complicated, and dangerous.

But not using real explosives has its costs because training with synthetic explosives isn’t as accurate. In court, a dog’s findings can often be discounted if it was not trained on real explosives, or if doubt can be cast on the dog’s findings based on the lack of training standards or other related issues.

A recent Supreme Court decision that permitted the findings of a drug-sniffing dog to be used as evidence shows that courts are slowly becoming more receptive to allowing canine-found evidence. In that case, a drug-sniffing police dog in Florida alerted his officer to the scent of drugs on a vehicle during a traffic stop. In a unanimous decision, Supreme Court justices ruled in Florida v. Harris that drug or bomb-detection dogs can give police probable cause to search private property if they alert officers to potential illegal activities.

MacCrehan says that dogs provide an important alternative to technological explosives detection. “Swipes are great for portals like airports, where people are going through and you can swipe the handle of their luggage and catch them in the act,” he says. “But if you had 300 people with swipes and instruments, they could work a building for a month before they could have found where the explosives were. The dogs can do it in a matter of 10 minutes.”