A Safer Way to Train Explosives and Narcotics Detection Dogs

Detection dogs in training at Auburn University College of Veterinary Medicine. Credit: Courtesy of Auburn University College of Veterinary Medicine

Dog trainers can no longer handle or expose dogs to real explosives and narcotics.

Trained dogs are exceptional chemical sensors, much better at detecting explosives, narcotics and other substances and even the most advanced technological devices. But one challenge is that dogs need to be trained, and training them to use dangerous substances can be very difficult and dangerous.

NIST scientists have been working to solve this problem using a material such as jello called polydimethylsiloxane, or PDMS for short. PDMS absorbs odors and releases slowly over time. Put it in a container with explosives or narcotics for a few weeks until it absorbs the odor, and you can then use it to train the dog safely to detect the real thing.

But a few weeks ago, and now, NIST researchers have developed a faster way to deploy PDMS by steam. In a journal Forensic Chemistry, they describe the heating compounds present in the explosives, causing them to release steam more quickly, then capturing the steam by PDMS which is maintained at cooler temperatures, which allows for easier absorption of steam. This two-temperature method reduces the time required to “charge” PDMS training assistance from a few weeks to a few days.

“Saving time can be critical,” said NIST research chemist Bill MacCrehan. “If a terrorist is using a new type of explosive device, you do not want to wait a month for the training to be ready.”

For this experiment, MacCrehan disseminated PDMS and dinitrotoluene vapor (DNT), which are low-level contaminants present in TNT explosives but the main odor that dogs respond to when they detect TNT. He also deployed PDMS with steam from a small number of TNTs. Co-authors at the Auburn University College of Veterinary Medicine then indicated that trained detection dogs responded to PDMS DNT training assistance that was infused as if they were truly TNT.


Scientists at NIST and the Canine Performance Science program at Auburn University College of Veterinary Medicine are working together on research that tests new methods for training dogs to detect explosives and narcotics. In this video, which shows the same set of experiments as those used in the NIST study, chief dog instructor Terrence Fischer set the test with dog instructor Jennifer Jankiewicz stating the dog response. If a dog, a Labrador retriever named Buddy, reminds a true sample by sitting next to him, he will be rewarded with a toy of his choice and time to play a little with another dog instructor. Credit: Used with permission from Auburn University College of Veterinary Medicine.

While the study focused on DNT as proof of concept, MacCrehan stated that he believed the two-temperature method would also work with other explosives and narcotics such as fentanyl. Some very strong forms of fentanyl that are inhaled can be harmful or fatal to humans and dogs. But by controlling how much steam PDMS absorbs, MacCrehan said, it should create a safe training tool for fentanyl.

Safe training aids are available. Some are prepared by dissolving explosives and applying the solution to glass beads, for example. “But most have not been widely accepted in the dog detection community because its effectiveness has not been proven,” said Paul Wagoner, co-author and co-director of the Canine Auburn Performance Science Program. “If you put explosives in a solvent, the dogs thought it really did detect the solvent, not the explosives.”

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 “heat stays hot and cool stays cold,” as the 1980s commercial jingle put this). He prepared some examples by placing DNT on the hot side, where his chemicals were heated to temperatures ranging from 30 to 35 degrees Celsius (86 to 95 degrees Fahrenheit) – too far in the temperature which will cause TNT to explode. PDMS is kept at 20 degrees Celsius, or about room temperature, on the other side of the charging station.

MacCrehan loaded a DNT-infused PDMS sample, which held its charge for several months, into perforated metal cans. He also loaded some cans and blanks – PDMS samples with no added steam. He was labeled with a can of code and sent to Auburn University.

Researchers at Auburn have trained a team of six Labrador crews to detect TNT using real TNT explosives. They then conducted a study to determine whether the dogs would be alert to the PDMS of the NIST sample as if it were real TNT.

The study was “double blind”: Both dog handlers also noted that scoring dog responses knew which containers had been prepared. This is important because dogs are very fond of body language. If the handler knew that the sample was prepared with DNT, they thought it was unintentional to signal the dog in the direction of its gaze, a smooth shift in body position or other simple gestures. And if those who took note knew where the sample was, they thought it could over-interpret the dog response.

Dogs are wary of all DMS-infected PDMS samples. They are not wary of vacancies, meaning they are responding to DNT, not to the PDMS alone. “They responded to the sample as if they were real,” Wagoner said.

Dogs do not respond as consistently to PDMS which is infused with a limited amount of TNT. However, MacCrehan explained that a very small number of TNTs that he used for this purpose were thought not to contain a sufficient amount of DNT to distribute the sample.

Looking ahead, MacCrehan will experiment with ways to prepare PDMS training equipment for safe TATP and HMTD explosives. These compounds are very stable and easy to explode, so having training aids that are safe for them will be more beneficial.

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

References: “Two-temperature preparation methods for PDMS-based dog training exercises for explosives” by William MacCrehan, Mimy Young, Michele Schantz, T. Craig Angle, Paul Wagoner and Terrance Fischer, October 15, 2020, Forensic Chemistry,
DOI: 10.1016 / j.forc.2020.100290

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