An Unusual Atmosphere is an atmosphere that possesses highly irregular or rare qualities.
Selected Unusual Atmosphere Types
- Doughnut Atmosphere
- Ellipsoidal Atmosphere
- Mobile World Atmosphere
- Rad World Atmosphere
- Ring World Atmosphere
- Roche Worlds Atmosphere
- Rogue Atmosphere
- Rosette World Atmosphere
- Sphere World Atmosphere
- Storm World Atmosphere
- Tent World Atmosphere
- Twilight Zone Atmosphere
Extreme Atmospheres: Some of the more difficult atmosphere types to explain and describe are the 'extremes', types A, B and C which equate to Exotic, Corrosive and Insidious.
- Whereas the Very Thin, Thin, Standard and Dense atmospheres are generally Earth-like in pressures with Earth-like gasses (Nitrogen-Oxygen-Carbon Dioxide mixtures) in a variety of amounts, the 'extremes' are terribly toxic, horribly lethal and utterly alien.
- The three types are really grades of lethality, and an A type and C type atmosphere may actually contain the same poisonous gas, just in different amounts. 
Lethality of Extreme Atmospheres Atmo. Code Class Name Danger Remarks A Exotic, Conventional Exotic Atmosphere DANGEROUS A gaseous mixture, which is unbreathable by mainline conventional life sophonts. B Exotic, Conventional Corrosive Atmosphere HIGHLY DANGEROUS Not only a dangerous gaseous mixture, but may have dangerous pressure, an temperature qualities in addition to corrosive (acidic) properties. C Exotic, Conventional Insidious Atmosphere EXTREMELY DANGEROUS Even more dangerous than a Corrosive Atmosphere, with persistently lethal properties that will kill most mainstream sophonts within minutes and destroy most protective equipment within two to twelve hours. D, E, F Exotic, Unusual Unusual Atmosphere DANGEROUS Unusual Atmospheres have livable respiration zones, typically at the heights or depths of a topography. They are rare worlds with very unconventional atmospheres such as Ellipsoid Worlds.
Basic Exotic-Extreme Atmosphere Types
- Extreme Low Temperature
- Very Thin, Low Temperature
- Very Thin, Moderate Temperature
- Very Thin, High Temperature
- Thin/Standard/Dense, Low Temperature
- Thin/Standard/Dense, Moderate Temperature
- Thin/Standard/Dense, High Temperature
- Very Dense, Low Temperature
- Very Dense, Moderate Temperature
- Very Dense, High Temperature
- Extreme High Temperature