Lufterators allow their user(s) to breathe underwater. It is described to be a T-shaped gadged, with the user placing the longer end into their mouth and placing the other piece over their lips and nose. It's use is described to be similar to sucking air through a small straw, causing the user's lungs to fall into a slower rhythm. Dex's modified Lufterator is Z-shaped.
Their first (and only) use described in the books occurred in Book 4: Neverseen, when Sophie, Fitz, Dex, Keefe, Biana, and Della use them to ride eckodons. Dex modified his Lufterator as to allow two individuals to use one at the same time, as Della accompanied the others without Mr. Forkle knowing (causing him to be one short). This requires the two users to keep their mouths close, causing Keefe to volunteer himself and Sophie. Dex countered by volunteering to share with Sophie as well, causing Mr. Forkle to decide that Dex and Keefe shall share.