I'm alone in my room, fingerpainting. I smell a fart. It wasn't me, but there's nobody else in the room... There is a multitued of possible problems here. Possible Problem 1) my farting muscles have reached a point where they can no longer feel farting. Possible Problem 2) my nose is smelling things that aren't really there (Could be several reasons for this, most likely poo particals trapped in nasal passages) or Possible Problem 3) there is somebody hiding in the room...farting...