Politeness requires that one should try not to make a noise when expelling anal gas. It similarly requires that one should not make a noise upon discovering expelled anal gases. Thus society continues in a mutual agreement to ignore the occurence.
My father used to say "you're like a fart in a colander" to indicate uselessness. I don't know why that has just popped into my head or even why I'm bothering telling you lot, but there it is.
I think it's about time we invented some sort of pants-catalytic-converter. We take pains to minimise every other bad smell our bodies produce, so it would be quite in keeping.