As anyone who has ever hung on to a sentimentally scented object can attest, smells can fade. But can you actively sniff the odor out of something? This was the question mental_floss posed to smell scientist and author of What The Nose Knows, Avery Gilbert, who insisted that, despite some caveats, the "hypothetical isn't really all that weird."
Gilbert explains over email that air fresheners designed to last a certain amount of time rely on the evaporation of chemicals that trigger receptors in your olfactory sensory neurons, and that could be applied to sniffing. "In principle, you could put a drop of scent in a sealed bottle and, with a pair of one-way valves and a nose mask, repeatedly sniff out the scented air," he says. "This would eventually deplete the odor. It might take a whole lot of huffing, but it could be done."
So could you stand over a stinky sock and sniff until it stopped smelling? "Probably not," Gilbert says. "Most scent-saturated materials (gym socks, White Castle boxes, etc.) tend to hang on to fragrance molecules pretty tenaciously, making it hard to get to absolute zero smell." Things like porosity, electrical charge, and chemical structure all affect how strongly an object hangs on to the molecules responsible for triggering smells in our brain. Also, the butyric acid that causes feet to stink happens to be especially "clingy"—but then again, so is the vanillin that causes vanilla odor.
When you chew gum until the flavor is gone, your nose gets a tiny portion of the blame. Odor molecules reach your olfactory neurons in one of two ways—either through your nostrils or through the roof of your mouth. When gum loses its flavor, "some of the volatile flavor compounds dissolve and get swallowed," Gilbert says. "But the rest are 'smelled away' through the nose."
Still, don't be afraid to stop and smell the roses. They have plenty of scent to go around.