Okay, I know where to work from now :)

Sterile does usually mean microbe free, which also means pathogen free. Though, it often ends up meaning no living microbes.

So, in terms of cleanliness, farts are low filth under normal circumstances, and also low microbes. In terms of poo that comes out with a normal fart, you’re talking amounts too small to be visible with the naked eye. Since any microbes would mostly be contained by or cling to those particles, they’re definitely in very small numbers.

In a normal fart, while wearing typical western style clothing (pants and undies, or at least undies) those particles are essentially never going to escape the filter the clothing provides. The only time that’s likely to change is when someone has diarrhea, as the splatter from a fart may be wet enough that even if it doesn’t feel like a shart, it could allow bacteria or other microbes a chance to grow and/or spread beyond the clothing.

The part of a fart that escapes is made up of a bunch of gasses (usually). The two “fragrant” components most people notice are hydrogen sulfide (rotten egg smell) and traces of scatole (the poo smell). Methane is usually odorless, and makes up the majority of most farts.

None of those chemicals is “dirty”. They don’t leave residue, they aren’t in a high enough concentration to cause harm once you’re smelling them, and don’t carry any germs/pathogens directly.

That being said, don’t lick your undies after a fart, and don’t lick someone’s butthole without a barrier. Because some of the bacteria in the gut is harmful if it gets into your mouth in significant numbers. E-coli in particular are wonderful little things to have in your guts, but hell anywhere else. It can, under the right circumstances, kill you.

That being said, the truth is that if you did lick underwear even immediately after a fart, there’s not going to be any more fecal matter on your tongue than you’d find in most processed foods (what with rodents loving stored produce and not having bowel control). And if you’re eating the booty when there’s visible poo, that’s on you lol.

Overall, a fart isn’t clean by any stretch of the Mendon meaning. But it also isn’t so filthy as to matter on a regular basis.

When it comes to the typical materials farts and poo are made of, beyond those that are the majority, I’d have to look the list up again. Which I’ll be glad to do if you want, since I have bookmarks saved on my laptop for such things (you’d be amazed how often this subject comes up). But be aware that it’s pretty boring as a list, even if you recognize the names of the components