Scent (in the context of K9 SAR) is not the same as smell. Scent has a smell, or odor, but when speaking of scent in the realm of working dogs, it is something a bit more physical. Scent is how dogs can do what they do. Their bodies have adapted to the collection and processing of scent for millennia.
Live Scent
Every person has a unique scent, to the exclusion of all other people. As we go about our daily routines, skin cells (along with other microscopic debris) are constantly being shed from our bodies. This debris contains minute portions of our sweat, hormones, personal bacteria, and so forth. These scent cells, often called “skin rafts” by SAR people, float around us on the air currents before eventually settling on the ground and sticking to surfaces that we pass or stay near. They also are carried upward by the thermal effect of our body heat, where they are caught up in the air currents that are always flowing (even if we can’t feel a breeze).
Our own experiments (and those of other respected handlers from around the SAR community) have indicated that properly trained K9s are even able to distinguish between identical siblings. Since a person’s unique scent is partly made up of the individual’s physical conditions (current health, hormones, etc.) as well as their specific reactions to environmental factors, this may account for the slight differences between the siblings.
Decomposition Scent
If skin rafts are shed by a living person, how does one detect a deceased person? Rafts are initially shed from a body just as in a live person. As the decomposition process begins, bacteria in and on the body begin to break down the tissues, generating and releasing gases as they go. These gases are caught on the air currents just like the skin rafts and are carried away from the body. Also, as decomposition continues, some of the tissue releases fluids that may seep into the ground or flow away from the body.
Scent Theory is the study of how these skin rafts, gases, and fluids behave in the environment over time. It is at the core of how we train and work. Airborne scent has many of the properties of a fluid. Over time, scent will flow downhill. Scent will evaporate. Moisture (like dew) will refresh scent. Passing cars will cause scent to flow into an eddy, as will scent on the water.
The Scent Article
Any objects that we wear or rest on or hold in our hands also pick up our scent. This object then becomes what we refer to as a “Scent Article.” It can be a piece of clothing, a hat, a shoe, a pillowcase, a hair brush, a toothbrush, a car seat or steering wheel. The possible scent articles are all around us, although for K9-SAR purposes some are better than others.
Before a scent-specific search takes place, the K9 handler(s) will collect one or more scent articles to use to let the dogs know the scent they are seeking.
If at all possible, always let the K9 handler(s) working the search collect their own scent articles. They know specifically what they are looking for.
If you are a parent of a toddler or a caretaker of a person at a higher risk of wandering, see the “Proactive…” section below.
The Scent Cone
As mentioned above, skin rafts (and gases in the case of a body) are carried along by the air currents that are always flowing (even if we can’t feel a breeze). In water, they float to the surface and are carried along by the breeze and any current as well.
The scent cone is an invisible triangle with its point at the source of the scent and the widening area downwind and/or downstream from the point. As the scent travels farther away from the source, it tends to spread across a wider area and naturally becomes more diffuse.
When a scenting dog first picks up the scent somewhere within the scent cone, they will work toward the stronger odor until reaching the source.
In a water search, air and water currents can result in more than one scent cone, which the dog and handler will have to work through to find the strongest scent. That point will be where the scent is breaking the surface of the water.
The Scent Pool
When there is little air movement or if a missing person has been stationary for a while, the scent components will coalesce around the body and form what is called a “scent pool.” As time passes, this scent pool expands and becomes more diffuse as it travels farther away from the source.
The scent pool can become quite large over time.
As in working a scent cone, a scenting dog will detect the edge of the scent pool and then start working toward the stronger scent.
A Proactive Step for High-Risk Individuals
If you are the caretaker (or you know someone with that role) of a person who is reasonably mobile but may be at a somewhat higher risk of becoming missing, such as:
- someone who can become easily confused on a walk
- someone who does not interact well with their environment
- someone who is normally outdoorsy but has some potentially incapacitating health issue like heart issues, diabetes, or is a fall risk
- a toddler
Did you know there is actually a simple proactive step you can take that could help if you ever find yourself needing a Search and Rescue K9?
You can create a nearly pristine scent article in advance and freeze it. This will help prevent having to try and find something or accidentally contaminating the scent article in the emotional chaos that is always prevalent when a loved one goes missing. The process is simple:
- Get a sandwich-size or larger sealable food-grade plastic bag (like a Zip-Lock storage bag) or an unused brown paper lunch bag. Do not touch the inside of the bag.
- If possible, have the person remove an article of worn clothing, place it in the bag, and seal it tightly. Underpants or socks are usually the best, but anything that was in significant contact with the skin will work. If the person is unable to do this by themselves, carefully do it for them but wear gloves or use just your fingertips to prevent touching the item or inside of the bag as much as possible.
- Write the person’s name on the bag and the date it was collected.
- Place the bag in your freezer.
The scent on this frozen scent article will remain viable for quite a long time, up to several months to a year or more, but should probably be replaced about every six months or so.