| A dog’s sense of scent is comparable
to a human’s sense of sight. Odor Sensitivity Dog’s
olfactory system is more than 10 million times as sensitive
as humans. Dogs have about 220 million scent cells,
compared to about 5 million in humans. 12% of a dog’s
brain is dedicated to scent.
Odor Lock
In the human being, the brain decreases or eliminates
the stimulus of smell to the brain after about ten
to fifteen minutes. 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.
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Olfactory Direction Location
A dog’s brain is able to discern which nostril has the
greatest concentration of odor. The greater amount of odor
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.
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. This is probably why narcotics
dogs are not fooled by coffee grounds or other destructors.
As long as the odor is present, the dog smells it.
What is Scent?
Scent is particulate matter, usually referred to as “rafts”
of dead skin cells constantly exfoliating (150,000 cells
/ hour). Scent can also be the oils of sweat (exocrine /
apocrine) or even residue from exhaled breath.
How does scent behave?
Though scent theory is just that, theory, experience shows
that it behaves like a "fog" or a "dust cloud"
following the human body's motion. 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)]
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 follow. Scent articles can be various items: Pillowcase.
T-shirt. Hat. Key, Wallet, checkbook. Sterile gauze swabbed
on scented item. Shoe inner sole (there is come argument
about this.) Garments, preferable inner not outer clothing,
but not panties. Porous is better than nonporous.
What make 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.
How do I collect scent guide?
When in doubt, don't. Let the dog handler collect it. If
the situtation dictates that you must collect one, choose
the correct item. 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. Remember that the person collecting
the article is contaminating it. Handle the items in as
short a time as possible; avoid leaning over the item. Use
gloves (I.e. latex) especially if you have to spend time
sorting or moving items around. Use clean tongs / tweezers
to pick up the item. If possible make multiple scent guides
form one item by, cutting it and bagging them separately.
Turn bag inside-out to collect item. Seal bag as soon as
possible after collecting item.
How do I make a scent guide?
Place a piece of sterile gauze over the item (car seat,
door knob, another scent article, etc.) Do not touch the
gauze. 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-locks. Law
enforcement staff sometimes requires brown paper bags. Do
not use a plastic bag with deodorant or any scent.
Label the tem: Include subject name, date and time collected.
Subject’s name. Any known contamination. When it is used,
note your name, when it was used, and circumstances of use.
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