For human life to survive you need 18-24% of the air to be breathable O2 (Earth's atmosphere has about 21% or 210,000 parts-per-million). Any less and you'll suffocate, any more and you'll get oxygen toxicity. From orbit, too little oxygen will make the atmosphere look red, too much will be yellow, and blue will be just right.
Oxygen requires at least 1 pascal of atmospheric pressure before it can begin to accumulate. If oxygen has accumulated but the pressure falls back to 0, any oxygen will be lost.
Habitability for plants and microbes to grow on a planets surface requires between 100,000 to 320,000 ppm. Habitability for animals and humans outside of a Habitation building is a narrower range between 180,000 and 240,000 ppm. The oxygen range in which a world is habitable for humans is really quite narrow. You will need to pay more attention to oxygen than to the other stats when trying to keep a world habitable.
As your oxygen level increases toward 210,000 ppm, the atmosphere will turn from red to blue. If it increases past 210,000 ppm, it will start to turn yellow. Learn more here.
You can't have more than 1,000,000 ppm oxygen on your world because 1 million ppm is 100% of the atmosphere composition.
Certain biosphere genes & species can also influence your oxygen levels.
The highest oxygen record on random planets is Epiver, which has a oxygen value of 999,759ppm.
|Carbon Fixer||-Oxygen, +Pressure|
|Hydro Generator||-Oxygen, -Water|
|Kelp Farm||+Oxygen, -Pressure, +Biomass (Biomass only), +Water (Biospheres only)|
|Solar Shade||-Temperature, -Biomass (Biomass only), -Oxygen (Biospheres only), -Credits|
|Orbital Mirror||+Temperature, -Water, -Biomass (Biomass only), -Oxygen (Biosphere only)|
|Biofixture Lab||-Pressure, +Biomass (Biomass only), +Oxygen (Biospheres only)|
|AtmoGen Suite||+Pressure, +Oxygen|
|Pocket Mine||+Pressure, +Oxygen|
|Electrolysis Plant||-Water, +Oxygen|
|Deep-Sea Collective||+Aquatic Species, +Oxygen|
|Hab Complex||+Habitats, +Oxygen|
|Hab Dome||+Habitats, +Water, +Biomass (Biomass only), +Oxygen (Biosphere only)|
|Transit Network||+Population, -Biomass (Biomass only), -Oxygen (Biospheres only)|
Note: If the player is playing with the Biosphere function, then whenever a building is supposed to produce biomass, it now produces oxygen instead (except for Comet Sling, it decreases heat instead than oxygen in Biospheres mode.)
Note: Gene effects are multiplied by the health of the species.
|Green Algae||+2 ppm/min|
- Atmosphere color is not due to the oxygen in the air, but to Rayleigh scattering or chemicals in the atmosphere (such as sulfuric oxide in Venus, or chlorine in real life Damu). TerraGenesis developers just linked atmosphere color to oxygen levels so first time players have a way to track its levels visually.
- Oxygen only requires a decimal of a pascal of pressure, but the game does not display decimal values, so it just shows the requirement as 1.
- In real life, microbes can survive with no oxygen at all. Earth’s atmosphere started out as 99% nitrogen and 1% carbon dioxide, but Cyanobacteria caused it to increase to about 1%.