While bomb-sniffing dogs provide an invaluable service, training them using actual explosives can be risky for both the canines and their handlers. A new process could help, utilizing a harmless polymer that quickly absorbs the scent of explosives.
First of all, there already are methods of training such dogs without directly exposing them to hazardous substances.
Explosives can be dissolved and diluted in a solvent, for instance, with the mixture then being applied to glass beads. According to NIST (National Institute of Standards and Technology) chemist Bill MacCrehan, however, it can subsequently be difficult to tell if the animals are detecting the scent of the explosives or that of the solvent.
One alternative involves placing the explosives in a sealed container, along with a rubbery organic polymer known as polydimethylsiloxane (PDMS). The PDMS proceeds to absorb the vapors given off by the explosives, then gradually releases them. This means that it can be used in place of the explosives, for training the dogs.
Unfortunately, though, it takes a few weeks of containment for the polymer to absorb enough of the vapors. This can be an inconveniently long time, particularly if terrorists have begun using a new type of explosive that authorities want to guard against as soon as possible.
With this limitation in mind, MacCrehan devised a process in which telltale compounds found within explosives are heated (safely) while the PDMS is simultaneously cooled. Doing so causes the compounds to release vapors at a faster rate, while also causing the PDMS to absorb them quicker. As a result, the polymer takes on the scent of the compounds within a matter of days instead of weeks.
In order to test his technique, MacCrehan started with a compound called dinitrotoluene (DNT) – this is a contaminant found within TNT, and it is the main odorant that TNT-sniffing dogs detect. Utilizing a "charging station" containing both a heating plate and a cooling plate, he proceeded to warm the DNT to about 35 ºC (95 ºF) while cooling PDMS samples to 20 ºC (68 ºF).
After a few days in the station, the samples were placed in perforated metal cans and sent to Auburn University in Alabama. In a double blind experiment conducted there, six trained Labrador retrievers successfully alerted their handlers to all of the DNT-scented samples, while passing over control samples of plain PDMS.
It is hoped that the technology could eventually also be used in the training of narcotics-sniffing dogs, as drugs such as fentanyl can be highly toxic when inhaled.
The research is described in a paper that was recently published in the journal Forensic Chemistry.
Source: NIST
