Authors: Edgar O. Aviles-Rosa1, Andrea C. Medrano2, Ariela Cantu2, Paola Prada-Tiedemann2, Michele N. Maughan3, Jenna D. Gadberry3, Robin R. Greubel4, and Nathaniel J. Hall1

1Canine Olfaction Research and Education Laboratory, Department of Animal and Food Sciences, Texas Tech University, Lubbuck, TX, USA; 2Forensic Analytical Chemistry and Odor Profiling Laboratory, Department of Environmental Toxicology, Lubbuck, TX, USA; 3DEVCOM-CBC; 4K9Sensus

Working Dogs have shown an extraordinary ability to utilize olfaction for victim recovery efforts in mass disaster events and missing persons cases. Although instrumental analysis has chemically characterized odor volatiles from various human biospecimens and from a whole-human scent (HS) perspective, to date, it is still not clear what constitutes HS from a detection dog perspective. Thus, the aims of this research were 1) to develop an automated human scent olfactometer (AHSO) to present HS to dogs in a controlled laboratory setting and 2) use the AHSO to evaluate dogs’ response to different scented articles and individual components of HS to determine the main constituents of HS dogs utilize. The AHSO was an adaptation of an olfactometer already validated by our lab. A human volunteer was placed in a clear acrylic box and using a vacuum pump and computer-controlled valves, the headspace of this box was carried to one of three ports in a different room. A computer program randomized distractor odors and HS presentation to ensure double blind testing. Dogs were trained to search all three ports of the olfactometer and alert to the one containing HS. In Experiment 1, the AHSO was validated by testing two dogs naïve to HS detection and five certified Search and Rescue (SAR) teams naïve to the apparatus. All dogs showed sensitivity and specificity to HS > 95% in the apparatus, indicating the AHSO was able to capture and deliver HS that naïve and trained canines detected. In Experiment 2, we trained six dogs to detect HS in the apparatus and tested their response to different scented articles exposed to the volunteer. We also tested their response to a breath sample and to a volunteer in the box when breath was exhausted outside the box. Dogs’ response rate to the different scented articles and to a volunteer in the box without breath was < 10 %. Dogs’ response rate to the breath sample was the greatest, but still lower than their response to the whole volunteer in the box. In Experiment 3, we further investigated dogs’ response to breath and to a volunteer in the box without breath with a different testing paradigm. In this experiment, dogs’ response rate to breath was 88% and was not statistically different than their response to the whole volunteer in the box. Dogs’ response rate to volunteers in the box when their breath was removed from the box was only 50%. Altogether, the data indicate that breath is a key component that dogs attend to in a HS detection task, and that removing breath from the headspace of the full human body significantly reduced the alert rate. These results have significant implications for SAR and human scent detection teams as it suggests breath is a critical constituent of HS. The data also indicates that the AHSO is a novel tool to further evaluate HS detection dog performance and olfactory perception.