Atmosphere

The Atmosphere Code is a UWP code to represent the breathing environment encountered on a world.

• It represents the mixture of gases and other elements that may be present on a sufficiently sized world or moon.
• Varying types of atmospheres require the use of protective clothing or masks.
• Very small worlds, planetoids, asteroids, and other small objects almost never have an atmosphere unless artificially modified using advanced technology.
• Tent Worlds are an example of a world ordinarily too small to contain an atmosphere, but artificially and technologically modified to possess an atmosphere using paraterraforming.

Description / Specifications

Some atmospheres require specific personal equipment for survival and protection.

World Atmosphere Classification Codes Table

Atmospheric Code Descriptions

Code	Specific Description	General Description	Pressure (ATM)	Remarks
0	Vacuum	Vacuum	< 0.001	Vacuum requires a vacc suit. The atmosphere has a pressure of less than 0.001 atmospheres, which requires the use of a vacc suit.
1	(Trace)	Vacuum	0.001-0.09	The atmosphere has a pressure of less than 0.1 atmospheres, which requires the use of a vacc suit.
2	(Very Thin / Tainted)	Vacuum	0.10-0.42	Very Thin tainted requires a filter respirator combination
3	(Very Thin)	Vacuum	0.10-0.42	Very Thin 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.
4	(Thin / Tainted)	Thin	0.43-0.70	Tainted requires a filter mask. The atmosphere contains an unusual taint such as such as disease, a hazardous gas mix, pollutants, or sulfur compounds which requires the use of a filter mask.
5	Thin	Thin	0.43-0.70	The atmosphere has a pressure of 0 43 to 0.70 atmospheres. The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
6	Standard	Standard	0.71-1.49	The atmosphere has a pressure of 0.71 to 1.49 atmospheres. The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
7	(Standard / Tainted)	Standard	0.71-1.49	Tainted requires a filter mask.
8	Dense	Dense	1.50-2.49	The atmosphere has a pressure of 1.50 to 2.49 atmospheres The atmosphere is a standard oxygen/nitrogen mix, which is breathable without assistance.
9	(Dense / Tainted)	Dense	1.50-2.49	Tainted requires a filter mask.
A (10)	Exotic	Exotic	varies	An unusual gas mix which requires the use of oxygen tanks, but protective suits are not needed.
B (11)	(Corrosive)	Exotic	varies	A concentrated gas mix or unusual temperature creates a corrosive environment, which requires the use of a Hostile environment suit or vacc suit.
C (12)	(Insidious)	Exotic	varies	The atmosphere is similar to a corrosive atmosphere, but extreme conditions cause the corrosive effects to defeat any protective measures in 2 to 12 hours.
D (13)	(Dense, high)	Exotic, Unusual	varies	Pressure at or below sea level is too great to support life but is breathable at higher altitudes.
E (14) †	(Ellipsoid) †	Exotic, Unusual	varies	The world’s surface is ellipsoidal, not spherical. Because the atmosphere remains spherical, surface atmospheric pressure ranges from very high at the middle to very low at the ends. Breathable bands may exist at some point within the range of pressure.
F (15) †	(Thin, low) †	Exotic, Unusual	varies	The Ellipsoid World is large and massive, with a thin atmosphere which settles to the lowest levels of the terrain. The atmosphere is unbreathable at most altitudes except the very low ones (as in depressions or deep valleys).

^† - NOTE: In MgT and T5, Atm type E is "Thin, Low", and Atm type F is "Unusual", which includes (but is not limited to) Ellipsoidal atmospheres.

Protective Measures Based on Atmosphere

The various atmosphere types require specific personal equipment for survival and protection.

• Codes 0 and 1: No atmosphere and trace atmosphere require use of a vacc suit and associated support equipment.
• Codes 2, 4, 7, and 9: Tainted atmospheres require the use of specialized filter masks.
• Codes 2 and 3: Very thin atmospheres require the use of compressors to insure sufficient oxygen to breathe. The tainted very thin atmosphere requires a combination respirator/filter mask for survival.
• Codes 4, 5, 6, 7, 8, and 9: Thin, standard, and dense atmosphere are breathable without assistance unless tainted.
• Codes A, B, C, D, E, and F: Exotic atmospheres require the use of oxygen tanks, but protective suits are not usually required unless corrosive or insidious.
• Code B: Corrosive atmospheres require the use of protective suits or vacc suits.
• Code C: Insidious atmospheres are similar to corrosive atmospheres, but will defeat any personal protective measures in 2 to 12 hours.
• Codes D, E, and F: represent "Unusual Atmospheres" with special conditions such as Ellipsoid Atmospheres.

Basic Atmosphere Types

Combinations of the below atmospheres may exist and are not comprehensively listed:

1. Corrosive Atmosphere
2. Dense Atmosphere
3. Ellipsoid Atmosphere
4. Exotic Atmosphere
5. High Pressure Atmosphere
6. High Temperature Atmosphere
7. Insidious Atmosphere
8. Low Pressure Atmosphere
9. Low Temperature Atmosphere
10. Standard Atmosphere (Tolerable pressure, temperature, constituent gases, etc. for conventional lifeforms)
11. Tainted Atmosphere
12. Thin Atmosphere
13. Trace Atmosphere
14. Vacuum (Interstellar Medium)
15. Very Thin Atmosphere

History & Background / Dossier

All industrial societies must gain an expanded understanding of atmospheres, air pressure, atmospheric constituents, gas behavior, industrial pollutants, and other factors in order to build a successful, modern interstellar starfaring society of TL:10-12 or greater. The UWP is one of the external expressions of those expectations about atmospheric understandings within Charted Space.

Atmospheric Equipment

Some selected equipment used in nonstandard environments with nonstandard and unusual atmospheres include:

1. Air Tanks
2. Atmosphere Tester
3. Atmospheric Survival Suit
4. Ball, Rescue
5. Base, Advanced
6. Battle Dress
7. Beacon, Emergency
8. Body Pressure Suit
9. Cabin, Prefabricated
10. Combat Environment Suit
11. Combination Filter Mask-Respirator
12. Compressor
13. Extended Life Support Sytem
14. Filter Mask
15. Filter Respirator Combination
16. Filter Suit
17. Gauge, Depth
18. Gauge, Tank Pressure
19. Hazard Suit
20. Hostile Environment Suit
21. Locator, Inertial
22. Mask, Face
23. Mask, Filter
24. Mask, Protective
25. Oxygen Rebreather
26. Oxygen Tanks
27. Respirator
28. Regulator
29. "Sniffer" Bioscanner
30. Suit Air Conditioner
31. Suit, Protective
32. Suit, Protective, Heavy
33. Survival Bubble
34. Tent, Pressure
35. Vacc Suit

Basic Atmospheric Taints

Atmospheric taints are also known as irritants:

1. Atmospheres with an imbalance of Ammonia (NH3)
2. Atmospheres with an imbalance of Carbon Dioxide (C02)
3. Atmospheres with an imbalance of Chlorine (Cl2)
4. Atmospheres with an imbalance of Methane (CH4)
5. Atmospheres with an imbalance of Organic Taints
6. Atmospheres with an imbalance of Oxygen (02)
7. Atmospheres with an imbalance of Nitrogen (N2)
8. Atmospheres with an imbalance of Sulfur Compounds

References and Contributors

This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.

• 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.
• Geir Lanesskog. World Builder's Handbook (Mongoose Publishing, 2023), 64-68.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.
• Citation Missing - Mongoose Traveller Main Rulebook
• Marc Miller. T5 Core Rules (Far Future Enterprises, 2013), 409.
• Author & Contributor: Lord (Marquis) and Master of Sophontology Maksim-Smelchak of the Ministry of Science