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  1. 09 Apr '08 13:12
    i once had a brief debate with my brother in law, who is an over-the-top know-all chemical engineer, about how smell works. never got to the bottom of it, and my wife has made me promise never to raise science related issues with him because he just goes into a very boring lecture mode.
    the question is, does smell travel along with normal air circulation within a room, or can it somehow move fasted/ deeeper by some other mysterious medium?
  2. 09 Apr '08 14:24
    Originally posted by eamon o
    i once had a brief debate with my brother in law, who is an over-the-top know-all chemical engineer, about how smell works. never got to the bottom of it, and my wife has made me promise never to raise science related issues with him because he just goes into a very boring lecture mode.
    the question is, does smell travel along with normal air circulation within a room, or can it somehow move fasted/ deeeper by some other mysterious medium?
    All molecules are moving constantly (Brownian motion I think its called). That is how heat in a gas works. The result of this random motion is that in a room with no apparent wind or air movement, an molecules of anything including and air molecule or a smell molecule may get from one side of the room to the other quite quickly.
    If there is a slight breeze then it is simply that the average movement of molecules is in one direction however there are individual molecules zipping about in all directions.
    So yes, smells can travel faster than the apparent air circulation and no it is not mysterious.

    To observe something similar try dropping dye into water and watch how it disperses even when there is no apparent movement of the water.
  3. 12 Apr '08 09:44
    Process of diffusion: "particles will move from an area of high concentration to an area of low concentration until the concentrations are equal"

    So no, it has nothing to do with air currents etc. - the molecules which cause the smell are compelled to move by this process, which occurs in virtually all fluid media.
  4. Donation kirksey957
    Outkast
    12 Apr '08 16:06
    One interesting thing about smell is that a particular smell is not determined by the molecules that enter the nose, but rather by the order in which the noci receptors "fire."
  5. Subscriber coquette
    Already mated
    12 Apr '08 17:44
    Light a match and the "smell" can be detected faster than the drifting streams of air would carry the molecules because the individual molecules are really traveling fast, real fast.
  6. 13 Apr '08 09:34
    Originally posted by darkbishop28
    Process of diffusion: "particles will move from an area of high concentration to an area of low concentration until the concentrations are equal"

    So no, it has nothing to do with air currents etc. - the molecules which cause the smell are compelled to move by this process, which occurs in virtually all fluid media.
    Thanks everyone for contributing to the topic.
    I guess that indoors is one situation, but outdoors the wind direction is paramount, otherwise all those animals using smell as an alarm system would be wiped out. Presumably the wind causes a direction-ality to the dispersion?
  7. 13 Apr '08 11:41
    Originally posted by eamon o
    Thanks everyone for contributing to the topic.
    I guess that indoors is one situation, but outdoors the wind direction is paramount, otherwise all those animals using smell as an alarm system would be wiped out. Presumably the wind causes a direction-ality to the dispersion?
    Exactly. You have the diffusion super-imposed on top of a translation at the wind velocity. Some particles might make it upstream, but far more will go downstream.
  8. 14 Apr '08 15:23
    Originally posted by mtthw
    Exactly. You have the diffusion super-imposed on top of a translation at the wind velocity. Some particles might make it upstream, but far more will go downstream.
    so how long before we have smellavision then? im guessing that a device can be created to fool the nose into sending smell-related messages to the brain, just think of the possibilities.............
  9. 14 Apr '08 16:22
    Originally posted by eamon o
    so how long before we have smellavision then? im guessing that a device can be created to fool the nose into sending smell-related messages to the brain, just think of the possibilities.............
    Well, I can think of three methods:

    1. A device that synthesizes smell molecules.

    Problems: There are many types of smell molecules ; some of them are rather difficult to synthesize.
    It would mean your smellavision is a ultra miniaturized, super complex , fully automatic chemical lab.

    2. A device that stores and releases smell molecules.

    Problems: As above, there are many of these molecules, I don't think it is feasible. Plus, if you accidently release the molecules - kiss your sinuses goodbye ;-)

    3. A neural chip that, instead of fooling the nose, fools your olfactory center in the brain.

    Problems: We are still far away, technologically.


    So, no, I don't see a smellavision in the near future.
    Sorry
  10. 15 Apr '08 14:12
    Wow! Nine posts about how smell travels in a confined space and not a single fart joke. Way to go gang!
  11. Standard member sonhouse
    Fast and Curious
    15 Apr '08 14:25
    I was thinking about something that may be related to smell.
    I work midnight to 8 shift, just started. Anyway I had this banana and it was getting on towards not rotton but at the end of its edible time.
    So I take a bite, and I get this sensation in my mouth like it was a smell, a definite banana kind of thing but a cross between an actual smell and a sort of feeling of banana vapor in my mouth. Anyone had that happen? Any explaination? It wasn't rotton, just a few more days and you would not want to eat it. I have had that happen before, this half smell, half feeling kind of thing. Maybe some of the vapor going into my nose from the inside?
  12. 15 Apr '08 15:02 / 2 edits
    Originally posted by sonhouse
    I was thinking about something that may be related to smell.
    I work midnight to 8 shift, just started. Anyway I had this banana and it was getting on towards not rotton but at the end of its edible time.
    So I take a bite, and I get this sensation in my mouth like it was a smell, a definite banana kind of thing but a cross between an actual smell and a sor smell, half feeling kind of thing. Maybe some of the vapor going into my nose from the inside?
    smell and taste are closely connected, the chances are that you smelled the banana with your nose and at the same time tasted the banana vapour being given off due to its advanced age. sounds like some of those stinky french cheeses. next time you have a bad cold, try it out again, this time without your nose being involved. just taste that lovely banana gas
  13. 07 May '08 21:53
    Not for much longer

    What happens to farts? How does the smell decrease with time.

    Does your nose get used to it and 'tune out'

    or

    do the odour compounds slowly break down by oxidation (or some other mechanism) in the air?

    And what are the odour compounds?