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If you've ever farted in the shower, you know that they smell REALLY bad in there, but why is that?

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Even if you’re not a huge fan of talking about it, and to be clear I don’t understand that impulse, you, me, and everybody else farts, and the average person does it up to 20 times a day.

Most farts don’t smell that great even on a good day, but if you’ve ever let one rip in the shower, you might know that they can smell worse in there. Why?

Nothing wakes you up in the morning like a nice, hot noseful of your own butt gas. We’ve talked quite a lot about farting before on SciShow, and if you want to know what makes them smell the way they do, you can watch our episode about it. Mostly, you can thank bacteria living in your gut, which produce a bunch of lovely, gross-smelling chemicals.

And the smell just seems to get worse when you take a shower. Some of that is because you’re stuck in a closed space and there’s nowhere for you or the gas to go, unlike if you farted in a nice open field or while you’re traveling down an escalator. The main reason it smells especially bad is because of the added humidity.

Your sense of smell is super important. It helps you figure out if your food’s gone bad, if there are gas leaks, or if there’s a fire nearby, so researchers have been trying to better understand it. In one experiment, they put 75 volunteers in a room and they changed the room’s humidity and air pressure to learn how different conditions affect how we smell things.

They did not make the subjects fart, although that would've been amazing and I hope somebody does that study someday. But they did introduce other odors, and they found that when the room was more humid, the volunteers could smell much lower concentrations of the odors. Essentially, their sense of smell got better when there was more water vapor in the air.

Not many studies have looked at that before, so the scientists weren’t really sure why this happens. One possibility is that the water vapor helps the molecules that make up the smell interact with receptors in your nose. Another idea is that the gas particles bind to the water vapor, so the air acts like a sponge and can hold more smell than regular, dry air.

When you take a hot shower, your bathroom fills up with steamy water vapor, so one way or another, that gross smell ends up being a lot stronger. It also probably doesn’t help that you aren’t wearing clothes, so there isn’t any fabric to absorb the smell or lock it in, but, as you probably would guess, researchers have not done many studies on that yet. Either way, the next time you feel the need to let one go, you might want to wait until you’re out of the shower.

You probably will thank yourself. Though, at least it’s just you in there, no one else has to know. Thanks for asking, and thanks to our patrons on Patreon for helping us answer all sorts of weird, awesome questions like this one.

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