Question

What is the role of diffusion in removing volatile compounds from an enclosed space? I'm trying to convince my coworker that even "just a little bit" of fragrance used in our enclosed office remains for some time, even when she can no longer smell it.

Answer 1

Diffusion just means that you had a high concentration then you stuck it in a larger volume container and it then dispersed throughout that container. You could say that it was still in the room it's just not floating around as a vapor as much because either it's absorbed into the surroundings or it's so dilute your nose could not detect it.

Answer 2

Thanks Shama. I remember hearing something about diffusion with regard to how gases move from a smaller space to a larger space or vice versa and don't remember details. Isn't it true that it would take longer for gases in a smaller container to move to a larger space or do I have that backwards?

Answer 3

Human senses are much more relevant than diffusion here. The key point is that you can smell it even when your coworker can't. That's not (usually) because there actually is more perfume near you than her, but because the human nose "adapts" in the same way your eye adapts to varying levels of illumination, e.g. becomes much less sensitive to light during the day than at night. Her nose, being first exposed to the perfume, and exposed at a higher level, adapts earlier than yours, so she simply stops noticing the smell before you do. (You will, too, given enough time.)

That may be a more profitable approach for you to take anyway. If you can both agree to fully respect each other's sense experience, and realize that through no conscious choice it may well be quite different, then you may be able to come to some mutually respectful agreement.

But to answer your actual scientific question, diffusion cannot remove substances from an enclosed space at all. Diffusion refers just to the random drift of molecules inside the enclosed space, which will cause them to fill up the enclosed space evenly after enough time. If you have an opening -- a window or door -- then perfume will diffuse out of the space into the outside, and THAT would remove perfume from the space. Or you may be thinking of adsorption or absorption, where the perfume might get "stuck" on a solid surface or dissolve in a liquid, and thereby be removed from the space.