A Very Thin Atmosphere is a type of atmosphere which requires a respirator.
- The atmosphere has a pressure of 0.1 to 0.42 atmospheres, which requires the use of a respirator to ensure sufficient oxygen.
An atmosphere rated as Very Thin has a mean surface pressure ranging from 0.10 atm to 0.42 atm.
Surface Pressure & Water Properties
History & Background (Dossier)
At altitudes above 4,000 meters on Terra, such as most of the Tibetan plateau, the oxygen content in every breath full drops almost to 50%, whilst above 7,000 meters (the peaks of the Himalaya mountains) the lack of available oxygen reaches lethal levels. This extreme altitude on the 'roof of the world' is equivalent to the IISS Scout Code atmosphere of Very Thin. For most explorers, respirators or oxygen masks will be required in this type of environment. 
References & contributors (Sources)
- Marc Miller. Worlds and Adventures (Game Designers Workshop, 1977), 5.Marc Miller, Robert Eaglestone, Don McKinney. Worlds and Adventures (Far Future Enterprises, 2019), 5.
- J. Andrew Keith. Exotic Atmospheres (Game Designers Workshop, 1983), 1-16. (Special Supplement 2 from the periodical Journal of the Travellers' Aid Society 17)
- Marc Miller. Referee's Manual (Game Designers Workshop, 1987), 22.
- Joe Fugate, J. Andrew Keith, Gary L. Thomas. World Builder's Handbook (Digest Group Publications, 1989), 64-68.
- Terrance McInnes, Dave Nilsen. World Tamer's Handbook (Game Designers Workshop, 1994), 11-17.
- Jon F. Zeigler. First In (Steve Jackson Games, 1999), 70,72.
- Paul Drye, Loren Wiseman, Jon F. Zeigler. Interstellar Wars (Steve Jackson Games, 2006), 125-6.
- Gareth Hanrahan. Core Rulebook (Mongoose Publishing, 2008), TBD.
- Marc Miller. T5 Core Rules (Far Future Enterprises, 2013), 409.
- Paul Elliott. The Universal World Profile (Zozer Games, 2016), TBD.
- Traveller Wiki Editorial Team
- Author & Contributor: Lord (Marquis) and Master of Sophontology Maksim-Smelchak of the Ministry of Science