Ass filter. (anal emissions catalytic converter)

A device for preventing the smell from some people's asses from affecting the productivity of others. Manufactured and fuelled by the Anal Emmisions Commission.

This is neccesary for those who eat a great deal of feet. In particular, Hobbit's feet.

"That stinks you shit, get a fucking ass filter!"
"You've got bowel rot! At least get an ass filter you stinky novice"