Hyperoxic Trimix
The National Association of Underwater Instructors (NAUI) uses the term "helitrox" for hyperoxic 26/17 Trimix, i.e. 26% oxygen, 17% helium, 57% nitrogen. Helitrox requires decompression stops similar to Nitrox-I (EAN28) and has a maximum operating depth of 44 metres (144 ft), where it has an equivalent narcotic depth of 35 metres (115 ft). This allows diving throughout the usual recreational range, while decreasing decompression obligation and narcotic effects compared to air.
GUE and UTD also promote hyperoxic trimix, but prefer the term "TriOx".
Other divers question whether this proliferation of terminology is useful, and feel that the term Trimix is sufficient, modified as appropriate with the terms hypoxic, normoxic and hyperoxic, and the usual forms for indicating constituent gas fraction.
Read more about this topic: Trimix (breathing Gas), Blending