Grâce à la liberté dans les communications, des groupes d’hommes de même nature pourront se réunir et fonder des communautés. Les nations seront dépassées.
Friedrich Nietzsche (Fragments posthumes XIII-883)

Détection olfactive

Comment les chiens "voient-ils" avec leur nez





Non seulement nous ne sommes pas toujours en train d'utiliser notre odorat, explique Alexandra Horowitz, mais lorsque nous l'utilisons, c'est souvent parce qu'on sent une bonne ou une mauvaise odeur: il s'agit rarement d'une simple source d'information. Les odeurs que nous percevons la plupart du temps sont soit agréables soit répugnantes, très peu ont un caractère aussi neutre que notre vision... de même que nous voyons le monde, le chien le sent.

Il y a deux conduits aériens dans la truffe (entre 2.000 et 3.000 millions de capteurs, contre 6 millions chez l'homme) : l'un pour respirer, l'autre pour sentir le monde environnant, percevoir les mouvements, ou encore faire la différence entre amitié et hostilité. Plus impressionnant encore, le nez du chien l'aide à voir des choses qui ne sont plus ou pas encore visibles: il détecte ce qui a eu lieu plus tôt (la voiture garée à un emplacement quelques minutes plus tôt) et ce qui n'est pas encore arrivé (une personne qui tourne au coin de la rue).

Nous sommes peut-être capables de remarquer que quelqu'un a ajouté une cuillère de sucre à notre café, mais le chien peut détecter cette cuillère de sucre dans l'équivalent de deux piscines olympiques.

Mais l'être humain aussi a du flair ! 
Très instructif "De la molécule à l'odeur".



Utilisation et utilité du dispositif STU-100
Lauryn E. De-Greeff et Kenneth G. Furton - Collection and identification of human remains volatiles by non-contact, dynamic airflow sampling and SPME-GC/MS using various sorbent materials, in Anal Bioanal Chem (2011) 401:1295–1307









Individual human scent as a forensic identifier using mantrailing  - Forensic Science International, Vol 282, January 2018, pp. 111-121 LeifWoidtke, JanDreßler, CarstenBabian

Individual scent article allows mantrailers to differentiate an odour trail.
Saliva as well as DNA extracted from whole blood are sufficient as a key stimulus.
Mantrailing appears as a reliable and useful tool for law enforcement authorities.

Abstract

Specially trained dogs have long been used by law enforcement agencies to help in criminal investigations and in searching for missing persons. Still, it is unclear which components of human scent released into the environment contribute to successful searches of individuals. In this study, saliva and axillary sweat samples were taken from a total of 190 people. Additionally, DNA was extracted from whole blood of seven different people and used as an odour sample as well. Overall 675 tests (trails) were performed during a period of 18 months. The ability to track individuals with the odour samples mentioned above was examined with seven dogs, four of which were specially-trained dogs (mantrailer) from the Saxony Police. Results indicated that specially-trained police dogs can track a person with an average success rate of 82% and correctly identify the absence of an odour track with an average success rate of 97% under various conditions. Private rescue dogs were less successful with an average success rate of 65% and 75% respectively. These data suggest that the potential error rate of a well-trained handler team is low and can be a useful tool for law enforcement personnel. Saliva, as a reference odour source, was found to be particularly suitable for the search. The results of the study suggest that the components contained in axillary sweat, saliva and DNA extracted from whole blood are sufficient, serving as a key stimulus for individualized searches.
(...)

Conclusion

In this study mantrailer dogs were tested under real police operating conditions. With a scent article from a person, they could follow the individual human scent trail of that person statistically highly significantly. Furthermore, they differentiate highly significantly between the presence and the absence of an odour trace using a scent article containing human scent. The best results were achieved with scent articles using saliva and sweat as an odour source. Additionally, highly significant results were obtained with scent articles from wet DNA samples. These findings may provide valuable information for the practical work of dog handlers for selecting suitable scent articles. The study shows that the success rate was higher depending on training method and operational experience level of the teams and for this reason only well-trained and certificated teams should be used in criminal proceedings. It has been shown that well-trained mantrailing-dogs can be in principle a reliable and useful tool for law enforcement authorities.