Dezember 12


Scent differentiation in a detection dog training


3rd Expert Conference of Rescue Dogs in Civil Protection and Missing Persons Search on September 24/25, 2022, in Künzelsau, Germany.


Their contribution of the speaker Jörg Zintl - Topic: Scent differentiation in detection dog training.
About Jörg Zintl: He is a trainer in customs dog training, at the General Customs
Directorate, Directorate IX, in Neuendettelsau.

Prior to my publication, I contacted Mr. Zintl and informed him that I would like to write a blog post about his presentation at the professional conference.
This resulted in a constructive exchange of views via email.

Mr. Zintl advised me that both his talk, and his correspondence with me, were solely as a private individual. He explicitly did not speak for the General Customs Directorate or the Customs Dog School, nor in his capacity as a customs dog trainer. Accordingly, his remarks are not official statements of the agencies and represent only his personal views.
His presentation at the conference was made at his own expense and without official assignment.

As to the content of his presentation:
I was a participant in this conference, sat in the audience and was naturally interested in this contribution.Jörg Zintl explained the practical training of sniffer dogs and how they are trained in the context of odor differentiation.
He said that there are two possibilities:

1. Training on a scent complex
2. The training on an odor component

He showed both possibilities in the following light picture and listed the pros and cons of both possibilities.
He addressed the selection of target scents, i.e., a planning that must be done before training a scent dog. In his opinion, there are initially two options for this at the current situation:
The scent component and the scent complex.
As he outlined in a slide of the presentation, both options have advantages and disadvantages, respectively. When training using a specific odor complex, he had listed, altered compositions may not be detected.
That was the point in the lecture that I could not and would not agree with.
Therefore, I would like to explain this in a little more detail in this paper.
Different explosives in turn have different components and compounds from other explosives and mixtures.
I therefore recommend initial conditioning on the actual finished substance (not just a component of it) and without a marking agent.The explanation for this is that the dog can selectively smell the individual components of an explosive and it stores the overall odor composition of the respective explosive as a kind of general
odor pattern in its olfactory memory.
Therefore, all explosives in their entirety and industrial/manufacturing composition are always to be trained
and conditioned and not only the individual basic substances or components of the compounded explosives.
In the case of explosives consisting of mixtures, there is usually only a smaller tolerance in the mixing ratios, because otherwise these could trigger an unwanted chemical or physical reaction.
However, this cannot be generalized to all explosives, as the practice of the assassins has shown. Therefore, it is always advisable to condition these substances on the finished product/substance or on the finished composition.
It can be helpful during the initial conditioning if different explosives or explosive substances, which are based on the same composition, are trained one after the other.
The 2005 study Formation of an Olfactory Search Image for Explosives Odors in Sniffer Dogs by Irit Gazit, Allen Goldblatt & Joseph Terkel demonstrates that sniffer dogs create "olfactory images" for themselves via a specific composition. The more often this composition is trained, the more certain and possible the success rate will be even with similar compositions.
The ability to separate complex odor mixtures elementally is critical for explosives detection dogs that must detect explosives when they are buried, concealed, and/or covered with masking odorants.HME`s (Homemade Explosives) can consist of an almost unlimited number of components that create complex odor mixtures. For
example, ammonium nitrate can be combined with a variety of organic compounds from fuels, such as fuel oil, as well as powdered sugar and other organic materials. This makes the olfactory target a highly variable odor mixture.
This odor mixture is also influenced by subsequent factors such as evaporation behavior and the concentration of the relevant substances in the gas phase, and are always dependent on a wide variety of factors in this regard:

Type of substance and its vapor pressure
Packaging - type of packaging
Whether other cargo is present in the cargo object to be
Is present, which has sorptive properties
The amount of cargo in the cargo object and the reduction of
the free air volume and the associated Restrictions on air
The size of the cargo object and the free air volume
Construction of the cargo object, geometry, air exchange rate
with the environment, etc.
Position of the hidden target material.
Transport conditions such as temperature, vibration, exposure time

Another very interesting study on this topic is:
Odor mixture training enhances dogs' olfactory detection of Home Made Explosive precursors by Nathaniel J.Hallab and Clive D.L.Wynneb from 2018.

Taken together, the results of this study suggest that to achieve optimal performance in detecting an odor target with highly variable and complex compounds, dogs must be trained with a variety of odor mixtures, with and without the base substance!
This contrasts with base-substance-only training, where dogs are trained to recognize only the primary oxidant and not "markers" or other masking odors added. Some research suggests that these base-substance-only procedures are not optimal.
Example: Dogs trained purely on potassium chlorate do not automatically detect potassium chlorate-based explosives and mixtures as well.
The ability to identify a critical oxidant (such as AN) in a complex odor mixture is likely influenced by previous experience and training experience.
As mentioned earlier, there are some explosives that have the one basic substance in common, but still have other additional substances in dosage and quality. This always leads to an individual mixture and smell composition and is stored in the dog brain also in each case in these mixture ratios in such a way.The dog can smell the individual components. In the scientific literature it is reported that by the presence of a further substance or several substances, the olfactory perception is disturbed.
One theory is that competition may occur at the binding site of olfactory receptors. If two substances bind to the same receptor and one of them has a higher affinity to the receptor, the olfactory impression of the other substance can be altered or completely blocked.

There is clear confirmation of this in several studies. The study by Lucia Lazarowski, David C. Dorman from 2013: Explosivedetection by military working dogs: Olfactory generalization from components to mixtures, clearly describes that training dogs on individual substances is not sufficient to reliably indicate substance that has this substance as a component.
Therefore, training on mixtures of explosives is always required for safe training and work.
Various explosive mixtures are only available locally because they are illegally manufactured there, and therefore can vary greatly from region to region. Explosives commonly found in IEDs include organics (e.g., 1,3,5-hexahydro-1,3,5-trinitrotriazine [RDX]; 2,4,6-trinitrotoluene [TNT]), inorganic oxidizers (e.g., ammonium nitrate
[AN], potassium chlorate [PC]), or a combination (e.g., Amatol-amixture of RDX and AN) (study by Kopp, 2008).In addition, the use of homemade explosives (HME) is more common than commercial and military explosives (study by Östmark et al., 2012). Consequently, the absolute and relative amounts of explosive precursors found in HME can vary widely.
A further challenge arises when the parent explosive has been further modified to include additional gelling agents (e.g., wax or petrolatum), fuels (e.g., diesel fuel or kerosene), or interfering extraneous odors (study by Kopp, 2008).
Therefore, most target odors (explosive odors) encountered by dogs in real-world conditions consist of a combination of many different substances (study by Harper et al., 2005), which may be different from the substances used in training.
Learning to respond to the detection of a trained odor may not generalize to the detection of new odor combinations. Therefore, it is important to include trained components to new configurations, such as mixtures of trained and untrained odors, in detection dog training.
In Laszowski's study, an experiment was done that isolated the actual components of an explosive by itself.
That is, without mixing them and then to physically separate them in an odor delivery device, but to deliver them as a common air stream to the detection dogs, which led to a later reliable indication of the actual explosive mixture.
The reasoning in his presentation that it doesn't matter if you put out a preparation without gloves because the perpetrator may not have been wearing any either, I don't think is correct either. It is also subject to the laws mentioned below.
Human adhesives are also subject to different chemical conditions and outgassing, etc. They do not have the manufacturing-related long outgassing phase.Typical human inherent odors volatilize, evaporate, or change in
consistency relatively quickly and differently than explosives.

Referring to the studies reported in the book Human Scent Evidence by Paola Prada, it can be said that human odor is composed of:

- Main odors: the smell of our skin and body produced by bacterial
- Secondary odors: the smell produced by what we eat, by the
deodorants and detergents we use
- Tertiary odors: produced by the environment in which we live

Not all people are the same: it is already known that there are differences between men and women. In addition, science shows that Asian populations emit a less intense and chemically different odor than Caucasian and African populations (which rank first in terms of the intensity of the odor emitted). These differences were
highlighted by analyzing the number of sweat glands-apparently present in the bodies of Asians compared to the number of the same present in Caucasians or Africans-and the different chemical composition of wax secretions in different ethnic groups.
It is no coincidence that army dogs in Vietnam could be trained to report only one ethnicity and ignore others.
Moreover, human odor changes significantly when we experience intense emotions or when we take specific medications. Thus, we find that the chemical composition of human odor varies and depends on how it differs according to ethnicity and emotional/health status.This means that our own personal human odor, which we leave on the preparation because we do not wear gloves, cannot be reliably identified by the dog because there are too many differences within the odor composition among people for the reasons mentioned above. This always leads to the great danger of misidentification.

After a further written exchange of the different points of view, Mr. Zintl concluded:
Conclusion Mr. Stingl:
"The detection works, why exactly is not 100% provable. And as long as we don't teach our dogs to talk, we can only speculate in detail."

My conclusion is:
"The training or the approach of Mr. Zintl is basically so possible. However, I consider the danger of false indications to be much too high when conditioning via a scent component."

I would like to take this opportunity to thank Mr. Zintl for the professional and very friendly exchange!
We have found that we are not far apart at all in the actual matter!
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