A Method for Controlled Odor Delivery in Olfactory Field-Testing.

A widely recognized limitation in mammalian olfactory research is the lack of current methods for measuring odor availability (i.e., the quantifiable amount of odor presented and thus available for olfaction) of training or testing materials during behavioral or operational testing. This research utilized an existing technology known as Controlled Odor Mimic Permeation Systems (COMPS) to produce a reproducible, field-appropriate odor delivery method that can be analytically validated and quantified, akin to laboratory-based research methods, such as permeation devices that deliver a stable concentration of a specific chemical vapor for instrumental testing purposes. COMPS were created for 12 compounds across a range of carbon chain lengths and functional groups in such a way to produce similar permeation rates for all compounds. Using detection canines as a model, field-testing was performed to assess the efficacy of the method. Additionally headspace concentrations over time were measured as confirmation of odor availability using either externally sampled internal standard-solid phase microextraction-gas chromatography-mass spectrometry (ESIS-SPME-GC-MS) or collection onto a programmable temperature vaporizing (PTV) GC inlet with MS detection. Finally, lifetime usage was considered. An efficient method for producing and measuring reliable odor availabilities across various chemical functional groups was developed, addressing a noted gap in existing literature that will advance canine and other nonhuman mammal research testing.

Canine olfactory detection of trained explosive and narcotic odors in mixtures using a Mixed Odor Delivery Device.

Like using a substandard calibrant to test and calibrate an instrumental detector, when detection canines are regularly exposed to less than optimal training material, their detection proficiency is diminished, risking the lives of their handlers and civilians they are intended to protect. This research examined canine detection proficiency to odor mixtures and the use of mixture training to improve said proficiency. Trained detection canines were tested on their ability to correctly locate their trained target odors, explosives or narcotics, in various mixtures from a series of blanks and distractor odors. After making base measurements, canines were trained on the target odor in mixtures using the Mixed Odor Delivery Device (MODD), which was previously developed to safely contain separated explosive components and deliver the mixed odor to a canine detector for training purposes. Headspace measurements, made using solid phase microextraction with gas chromatography/mass spectrometry (SPME-GC/MS), were also taken of mixture components in and out of the MODD to confirm that odor mixtures were accurately portrayed to the canines during MODD training. Following mixture training, canines were retested on the same mixtures. Results of the headspace analysis showed that the MODD did not alter the delivery of the odorants from the mixture components. As such, canines showed an improved proficiency in detection of target mixtures following mixture training, increasing the detection rate from 63% to 72% for pseudo cocaine mixtures and from 19% to 100% for explosive mixtures.

Generalization and Discrimination of Molecularly Similar Odorants in Detection Canines and the Influence of Training.

Operationally-deployed canine detectors are often trained on one or a limited number of materials representing a single target odor, and training frequently occurs using materials of a high purity grade in controlled scenarios with minimal other background odors. Conversely, in the field, canine detectors are expected to generalize and identify variations of the target odor, while discriminating from similar extraneous or background odors. This exemplifies the balance between generalization and discrimination required for effective canine detectors. This research explored the tendency for detection canines to generalize or discriminate between similar odorants. Two groups of related odorants were used in two separate studies; (1) odorants of similar functional groups with differing carbon chains, and (2) odorants of similar carbon chain length but differing functional groups. Within each odorant set, the effect of training was addressed by incrementally increasing the number of odorants each canine was trained to detect. Initially, discrimination increased with increasing molecular dissimilarity in both odorant groups. After further training on additional related odorants, generalization increased across the set of odorants of the same carbon chain length, but there were no significant changes in either generalization or discrimination across the set of odorants of the same functional group. The results suggest that the canines in this study were more likely to generalize across compounds of the same chain length with differing functional group than across compounds of the same functional group, but differing chain lengths. Furthermore, some variation in performance between individual canines indicated that the tendency to generalize differed with experience, breed, and other factors affecting olfaction.