If Dumb and Dumber has proved anything, it's that there is nothing more romantic than a flaming flatus. Yet, many people don't understand what's actually happening when they spark some butt air. Most assume the flame has something to do with methane. However, that's generally not the case, as the Today I Found Out YouTube channel highlights.
The air coming out of your fart oven is predominantly comprised of hydrogen and nitrogen. There's also carbon dioxide and "potentially a small amount of methane and oxygen" in there. Additionally, a very small amount of the very potent hydrogen sulfide is often present. It smells like rotten eggs.