Holding in farts is physiologically unwise because some gas vapor diffuses into the bloodstream and is eventually exhaled through the lungs.

“there's a tiny percentage of your fart which if you hold it in will go to your bloodstream go to the lungs and then be exhaled out so you will have breathe it you're going to breathe it instead of farting it if you don't fart it you will exhale fart so you will literally breathe out fart”