A fart contains hydrogen, some oxygen, and sometimes methane (not everyone produces methane) and will disipate into the air eventually so unless you have a new machine to reformulate the gas mass you will only be cleaning what you dealt.
don't know about farts..but I did a love seat today that when I moved the cushion there was some of the biggest..thickest human toe nails I have ever seen....for a minute there I thought someone trimmed there pet Teradactyl....the things clattered like marbles all the way threw the vacuum......thank god I use the bag-less type....there is no doubt in my mind if there was a bag.....on of them would of cut it wide open......