Scent and how K-9's use it to their advantage...
to be somewhere between 250,000 to more than 10 million times as sensitive as humans. Dogs have about 220 million
scent cells, compared to about 5 million in humans. Because of the increased amount of receptors 12% of a dog’s brain
is dedicated to scent. A dog uses its sense of smell in the same way as we use our eyes to view our surroundings.
Odor Lock
In the human being, the brain decreases or eliminates the stimulus of smell to the brain after about ten to fifteen minutes.
This can be best explained by the example of if you walk into a room that smells strongly of bleach, after a few minutes
you do not small it anymore, regardless of whether it is present for five minutes or five years. Dog’s do not do this.
They will continue to smell the bleach for as long as there are even an extremely small trace of it remaining.
Olfactory Direction Location
A dog’s brain is able to discern which nostril has the greatest concentration of odor. The greater amount of odor, even an
extremely small amount, is in the dog's left nostril it knows that whatever it is searching for is off to its left, and visa versa.
When the amount of odor is balanced in both nostrils then the animal knows that what ever it is searching for is in front of it.
Because of this ability, a well trained K-9 is able to use its sense of smell to follow a trail of a missing person knowing where
the person has walked and turned. Also they can tell the direction that the smell is coming from just using the wind currents.
Without this ability to determine direction of scent, the dog may not be able to tell which direction the scent is coming from
exactly, just that the scent is stronger in one area than another.
Odor Layering
When one first goes into the kitchen and someone is cooking chili, they can smell the chili. When the canine goes into the kitchen
though, it can smell the hamburger, the beans, the tomatoes, the seasonings, etc. The dog can break the chili into individual
layers of scent and can distinguish each of them as a unique odor in the mixture. This is probably why narcotics dogs
are not fooled by coffee grounds or other destructors. As long as the odor is present, even mixed with other items/chemicals,
the K-9 has the ability to smell the different components and can identify/alert on them.
What is Scent?
Scent is particulate matter, usually referred to as “rafts” of dead skin cells constantly exfoliating (150,000 cells / hour)
from all over your body. These scent rafts are even flowing at a rate of 120/m.p.h. up off of your head just due to your body heat,
so no matter where you go, or what you do, your scent is everywhere! Scent can also be the oils of sweat (exocrine / apocrine)
or even residue from exhaled breath.
These rafts actually have a chemical composition that is unique to the person that is expelling them. Because everyones diet,
bathing habits, chemicals used in cleaning clothes, areas of travel, etc, each person has a unique scent pattern.
Eventhough family members have similar genetics, habits, etc, a well trained K-9 should be able to distinguish the 'unique'
chemicals/odor of the missing person. Many K-9 teams may ask for family members to NOT be in the area of the search as
their dogs may find that the scent of a family member is 'close' but not exact to the missing person and it may cause the
dog to give a false alert.
How does scent behave?
Though scent theory is just that, a theory, experience shows that it behaves like a "fog" or a "dust cloud"
( ie. think of the Pig-Pen character from the Peanuts comic strip ) following the human body's motion but can act like
a liquid settling in low areas. Rafts of scent is believed to spread from 10' to 100' in diameter, or more. Gravity
does not effect the same way as dust however in that rafts will rise when they are warmer then their surroundings.
[Poikilothermic (changes to temp of its surrounding) Carried easily by wind & water Hydrophilic (likes water) Rises
and floats in water (salt & fresh)]. Many K-9 teams have noticed that scent works similar to the way that water does,
in the fact that it tries to flow into the lowest areas/depressions, and will flow downhill and is actually drawn to
water sources, creeks/rivers/lakes/etc.
When the weather is dry and hot, the rafts can dry out and not produce a lot of scent for the K-9 teams to work with,
but a light rain or higher humidity can actually rehydrate the rafts causing them to release greater amounts of their
scent. Heavy amounts of rain WILL wash away large amounts of scent, as it is similar to dust, but well trained K-9's
can still pick up the scent event after several inches of rain!
What is a scent article / scent guide?
A scent article can be defined as something that has the scent of the subject you are looking for. It is the single most
important factor in scent discrimination. Note that scent articles are often evidence and chain of custody must be followed.
What makes a good scent article?
A “good scent article” only has scent of the person you seek (and only that person.) That allows the dog to know whom to look
for and follow. Scent articles can be various items, including but not limited to: Pillowcase. T-shirt. Hat. Key, Wallet,
checkbook, clothing garments, preferable inner not outer clothing, but not underwear. Most teams prefer to use a Sterile
gauze swabbed on scented item as the porous gauze will collect the rafts for the dog to smell. Porous is better than nonporous
because it will trap the scent rafts IN the item, rather than just having some of the scent ON the article.
What makes a bad scent article?
A “bad scent article” doesn’t have the scent of the subject you are looking for, or has been contaminated with a competing
scent that confuses the dog. This contamination could be from “residual” sources, scent falling from the air or transferring
from another article, or “direct” meaning someone other than the person you seek touched the scent article. Example of bad scent
articles: Clean laundry. Shared clothing / linens. Item handled by someone other than the subject, something that has not been in
contact with the subject recently.
Many times a scent article is collected by a family member for the teams to use, without knowing that this is not an accepted practice,
so it is often the best to try to obtain an item yourself, but always thanking them for the effort!
How do I collect scent guide/article?
When in doubt, don't. Let the dog handler collect it or a trained member of the search team that has been taught how to properly collect
the scent articles without contaminating it too much. If the situtation dictates that you must collect one, choose an item that you believe
will contain a large amount of the persons scent. If the area has been thoroughly contaminated by previous search efforts or other family
members, look under furniture and between mattresses. Take precautions to avoid contamination of the item as the more scents that are on
the item, the more the dog has to work through to find the correct scent of the missing person. Remember that the person collecting the>br> article is contaminating it! Handle the items in as short a time as possible; avoid leaning over the item. ALWAYS use gloves (i.e. latex)
especially if you have to spend time sorting or moving items around to find a suitable article. Use clean tongs / tweezers to pick up the
item if possible as it will keep the item as far from 'your' scent rafts as possible. If possible make multiple scent guides form one item
by, cutting it and bagging them separately ( if the item is NOT needed by Law Enforcement as evidence ).
Most search teams recommend that you use a zip-loc style bag ( without perfumes ) as they are small and see through.
Seal bag as soon as possible after collecting item.
How do I make a scent guide/article?
Place a piece of sterile gauze over the item (car seat, door knob, another scent article, etc.) Do not touch the gauze
with bare hands, if you have to touch the gauze use latex style gloves for as short of time as possible. Place an open
zip-lock bag over the gauze like a tent (you can collapse the bag from the outside later to collect the gauze.)
Leave the items in contact long enough for the scent to transfer (depending on temperature, etc.) What kind of bag
should I use? Some prefer zip-locs. Law enforcement staff sometimes requires brown paper bags. Do not use a plastic
bag with deodorant or any scent as these chemicals can/may/will mask the scent of the person. Once a dog team has used
the scent article, it should not be used by any other team as the handlers and the K-9's scent are now on the item!
Label the items with a minimum amount of information including but not limited to: subject name, date and time collected,
any known contamination, when it is used. Please note your name, when it was used by you, and circumstances of use.
