K9 Chemistry: A Safer Way to Train Detection Dogs

Paul Waggoner, a co-author and co-director of Auburn’s Canine Performance Sciences Program. “If you put an explosive in a solvent, the dogs might actually be detecting the solvent, not the explosive.”

To test the two-temperature method, MacCrehan devised a PDMS “charging station” with a hot plate on one side and a cooling plate on the other (so the “hot stays hot and the cool stays cool,” as a 1980s commercial jingle put it). He prepared various samples by placing the DNT on the hot side, where the chemical was warmed to temperatures ranging from 30 to 35 degrees Celsius (86 to 95 degrees Fahrenheit) — well below the temperature that would cause TNT to detonate. The PDMS was kept a relatively cool 20 degrees Celsius, or about room temperature, on the other side of the charging station. 

MacCrehan loaded the DNT-infused PDMS samples, which hold their charge for up to a few months, into perforated metal cans. He also loaded several cans with blanks — PDMS samples to which no vapors were added. He labeled the cans with codes and shipped them to Auburn University. 

The researchers at Auburn had trained a team of six Labrador retrievers to detect TNT using real TNT explosives. They then conducted a study to determine if the dogs would alert to the PDMS from NIST samples as if it were real TNT.

This study was “double blind”: Neither the dog handlers nor the note-takers who scored the dogs’ responses knew which containers underwent which preparation. This is important because dogs are keenly attuned to the body language of their handlers. If the handlers knew which samples were prepared with DNT, they might inadvertently cue the dogs with the direction of their gaze, a subtle shift in body position or some other subconscious gesture. And if the note-takers knew which samples were which, they might over-interpret the dogs’ responses.

The dogs alerted to all the DNT-infused PDMS samples. They did not alert to the blanks, meaning that they were responding to the DNT, not to the PDMS itself. “They responded to the samples as if they were the real thing,” Waggoner said. 

The dogs did not respond as consistently to PDMS that was infused with limited quantities of TNT. However, MacCrehan explains that the very small amounts of TNT he used for this purpose may not have contained sufficient amounts of DNT to fully infuse the samples.

Looking forward, MacCrehan will be experimenting with ways to safely prepare PDMS training aids for the improvised explosives TATP and HMTD. These compounds are extremely unstable and detonate easily, so having safe training aids for them will be especially useful.

MacCrehan is a laboratory chemist, not an animal behavior expert. But despite his technological orientation, he is amazed by dogs. He estimates that they are 10,000 to 100,000 times more sensitive than the most sophisticated analytical instruments. “We are nowhere near having a hand-held gizmo that can do what they do,” he said.