Gas exchange unit
From Tardis Wiki, the free Doctor Who reference
A gas exchange unit was a type of device used and worn by the Slitheen family, separate from the skin suit. When the naked Bella let off an exceptionally long and loud fart, Grumma asked her if she was wearing her gas exchange unit, to which she replied that she was not and was just "really really" excited at the prospect of a human hunt. (AUDIO: Madquake)
