Make some scents out of today’s fact.
Do we only smell things when we inhale? Nope. Your sniffer is pulling in stink rays whether you’re inhaling or exhaling.
Inside your nasal cavity is the olfactory epithelium, which contains millions of microscopic receptors. These receptors are the little guys that become stimulated when odor molecules hit them. They send the smell message along the olfactory nerve to the olfactory bulb, which is located just beneath the front part of your brain. The bulb sends the smell signals to various portions of the brain, where they are interpreted and you recognize and react to the odor (“Mmmmm, cookies!” or “Gaaack! Take a bath once in a while!”)
Like any other body part, the receptors get tired, or as scientists describe it, “momentarily fatigued.” Once you’ve inhaled and they’ve detected an aroma, they need to rest and recoup. So, while you exhale, the receptors re-charge, and while you don’t smell things as keenly as you do when you inhale, you are still smelling things.
If the receptors smell a particular odor for an extended time, they become desensitized to it, and you don’t notice the aroma as much. That’s why a lot of folks don’t realize they have bad breath, or why visitors sometime notice that the baby needs changing before Mom does.