How Scent and Airflow Works

How do those dogs find missing people?

Remember PigPen from Charlie Brown?  He always appeared to have clouds of dust coming off of him wherever he went.  This is not far from the truth.

You have thousands of tiny pieces of your body leaving you every minute; 40,000 pieces to be exact.  These tiny cornflake like bits are called rafts.

They are made up of skin cells, hygiene products, bacteria, fungus, parasites, sweat, hormones, and enzymes. They are unique to each individual human.  Even skin rafts from identical twins are different.  These are what dogs smell.

Some skin rafts are lighter in air, easily carried by air currents.  Others are heavier than air,  alighting on vegetation or falling to the ground.

Dog Handlers pay attention to air currents.

Skin rafts are carried along currents of air like millions of fluffy dandelion seeds.

We pay attention to physics.  Warm Air rises

and Cool air sinks.  Cold and moisture make air heavier. Your skin rafts first leave your body at about 2mph up in the air traveling along the current of air your 98.6 degree F produces.

Without any air movement

scent diffuses evenly

Diffusion

But of course, there is always something making air move.

When things are perfect, scent moves predictably like this:

Laminar Flow

Objects and other factors often cause air to move like this:

Turbulent Air Flow

Turbulent air flow causes handlers and their canines to mutter choice words under their breaths.

Different Types of Airflow

Normal Daytime Air

When the ground heats up during the day time, air begins to rise.

Normal Nighttime Air

When the ground begins to cool, air cools and begins to fall. It flows downhill like water.

Coning Plumes

    • movement of scent from subject downwind in the shape of a cone
    • during cloud covered days or nights
    • travels long distances
    • ideal for dogs

A dog will run perpendicular to the flow of the scent crossing in and out of the scent cone zeroing in to its source.

Fumigating Scent

    • occurs in the morning before sunup
    • scents travel down valleys like water
    • subjects on a hill can be detected by dog down below
    • It is good to get dogs out before sunrise

Lofting Scent

    • Occurs after sun sets
    • The ground is cooling but aloft air is still warm
    • usually occurs in valleys first then other areas later on
    • Work dogs on the high ground in the evening

Fanning Plumes

    • at night in stable air
    • scent holds at the same elevation level without falling or rising
    • dog may alert across a drainage or canyon at the same level, but can’t find a person
    • Be sure to report your alerts as scent can carry

Pooling Scent

    • collects in an area like a pool of water
    • usually occurs in a low area
    • Occurs where there is little dispersal of scent by the wind
    • It hard for dog to follow a scent pool to the subject

Eddying Scent

    • circular air forms behind an object (turbulence)
    • prevents scent from traveling along prevailing wind
    • example: eddies form at a line of trees next to an open field

Looping Plumes

    • Occurs in clear sky or with high clouds
    • Occurs at midday, a high convection situation
    • scent rises, cools, falls, heats up, rises, cools, falls, etc.
    • Dog will alert by putting his head up, but will lose the scent.

Chimney Effect

    • Happens when air currents move straight up an object
    • alerts may occur nearby   -but-
    • scent may come down as much as several hundred meters away from the subject
    • This makes it nearly impossible for the dog to find the subject
    • You should check around tall objects in the area

Thermoclines

    • caused by significant temperature and humidity differences in short distances
    • changes in elevation
    • drastic changes in shade and sunny spots
    • creates a wall like barrier of scent

Handlers use their knowledge to help the dog find the subject

You are the brains.  Your dog is the nose.

A search dog team will prefer to search into the wind, often zigzagging into the wind on small areas. A canine team can also perform searches along parallel sweeps perpendicular to the wind in larger areas. Remember to search ridges when air is likely to be rising and down in drainages when air is likely to be falling.

Good Luck

A good book to read on the subject is:

Scent and the Scenting Dog by William G Syrotuck

Site note:

Hatch Graham’s 1979 Article on Convectional Turbulence and the Airscenting Dog

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34 Responses to “How Scent and Airflow Works”

  1. An EXELLENT post!

    • Thank you Jaime. A comment from my home state of New Mexico, although I live in Virginia now. It is good to hear from home. Also, I love your website. Anyone in Santa Fe need a nicely certified dog trainer check it out. http://www.citydifferentdogs.com/

    • Thank you for pulling this together, Jen! I just looked it over for review before I take my operational test. It is super useful, and I love all of Grom’s help in the illustrations, too!

  2. Great post! I’ve been studying various types of scent detection for a novel I’m writing, and this is a wonderfully clear presentation. (I also have Scent & the Scenting Dog and several other books.) I love the dog muttering choice words!

  3. What great information. Thanks for sharing!

  4. Pedro Julian Says:

    Me gustaria me envien info y si es posible alguna bibliografia referida a la discriminacion de olores.
    Me gustaria me envien info and if there is possible some bibliography referred to the discrimination of smells.

  5. Anonymous Says:

    great info here I’m glad I viewed it!

  6. Pamela Zachritz Says:

    Great thread! These are the best graphics I have ever seen on scent theory. Reminds me of petroglyphs. Many thanks!

  7. Jen –
    I love the clear communication of your and Grom”s drawings and descriptions of how scent works. I would love to use them to help some of our newer handlers and to explain some things to agencies we work with.
    Would you contact me concerning permission to use your work.

    Sue
    K-9s Taz and Gunner

  8. Michelle Limoges Says:

    I’d like to include this in our newsletter.
    could the owner of these terrific diagrams contact me at
    udcdoberman@shaw.ca
    Michelle – Search & Rescue Dog Association of Alberta
    Edmonton, AB, Canada

    • Michelle, I am the author of the diagrams. You may use them at your leisure. If anyone wishes to use them, you may contact me and I will send you the files.

      • I would love to have the diagram files. I mentioned in an above post we would like to use them to help educate handlers as well as some of the agencies we work with.

        Please send the diagrams to:
        k9srch@charter.net
        Thanks for being willing to share your talents with all of us.

        Sue
        K-9s Taz & Gunner
        Illinois-Wisconsin SAR Dogs

      • Jen, I too would LOVE to have a copy if possible. Thank you so much for sharing this valuable info with us!! Jan
        rocksoliddogs@aol.com

      • These are excellent diagrams. I am close to achieving certification as a K9 Nose Work instructor and would love to have the files as an aid for my classes. Thank you for making them available!

      • Sue Christensen Says:

        I am a handler with Illinois-Wisconsin SAR Dogs. I would like to have a copy of your files on how scent works to use with our new handlers and our presentations to law enforcement. Thank you. K9srch@charter.net On Oct 23, 2012 8:52 AM, “Hound and the Found” wrote:

        > ** > Valerie Casperite commented: “These are excellent diagrams. I am close > to achieving certification as a K9 Nose Work instructor and would love to > have the files as an aid for my classes. Thank you for making them > available!”

      • Cathi Carr-Lundfelt Says:

        rattlerjen: I am the training officer for Albany County Sheriff’s Search and Rescue in Laramie, Wyoming. I am very impressed with your diagrams and explanation. Would you please send me the files so we can use them for training purposes?

        Thanks, Cathi Carr-Lundfelt

      • Hi I would love to use these diagrams as well. Thanks in advance

  9. “Cold and moisture make air heavier.”

    Cold air is denser, but pilots are taught to beware “height, heat, and humidity” as these all make air less dense. Wikipedia on vapor density.

  10. rattlerjen-
    Would you please send me files for the “How Scent Works”. They will great assest in educating people.

  11. Hello,
    I am Jan and live in Holland. I am a SAR handler and i have a black maimois too. Amy I translate this article in Duch and use it
    thanks Jan

  12. Thanks for a wonderfully clear presentation. I’ve been involved in law enforcement K9 since the mid 70s and this easily the best bang-for-the-buck overview of scent dynamics I’ve seen. I will point K9 handlers to this link from this day forward.

  13. Venu Gopal Raja Says:

    Great, highly informative. thanks a lot.

  14. Anonymous Says:

    Good stuff. Now I want to know your opinion on hiding human scent from deer. What would your recommendations be for hunting on the ground or elevated in a tree? Which is better in early morning or just before sunset? How long does scent linger outside if you get inside of a hunting blind. I would imagine that things that make it difficult for a dog to track would also keep a deer from getting spooked.

    • I am not a hunter so do not know much about deer. Please help with this one hunters! Up in a tree probably helps as you are more likely to be getting chimney effect, lofting, and other effects that will make it difficult for the deer to pinpoint the source of the scent. Blinds will certainly slow the scent, but will not completely stop it. Hunters help me out on this one ;)

  15. Hi there folks. Those interested in the file may need to wait a week or so. I am in the process of updating the slide show so it may work in newer versions of PowerPoint. Paws up!

  16. Gale StJohn Marshall Says:

    Hi I am interested in getting permission to cote this info in a book.Its well written and easy for the beginner to understand.please contact me

    • Gale StJohn Marshall Says:

      Sorry my last comment should be quote not cote but my auto complete decided not to use it.

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