Breathable Atmosphere?

[Agraelgrimm (OP)]

What makes a breathable atmosphere here on Aurora? It is really hard to terraform something when you have no idea what is able to support life and not. Aside from, you know, temperature, atmosphere, water, etc, idk how to work this system. Could anyone explain that to me, please?

[ZimRathbone]

Oxygen pressure within your racial tolerances.

An inert gas to put the fraction of O2 to less than 30% . Usually Nitrogen, but I did by accident create an Oxy/Argon atmosphere once that seemed to work.  This was before C# tho, it may have changed since then. I must try an Oxy/He one for squeaky Aliens at some point.  Aestium & Frigidarium are inert for this purpose and change the temperature properties of the planet.

a little CO2 is OK (less than 2% I think) but too much becomes poisonous.

most of the others are poisonous, even in very small proportions, and have to be removed.

In the VB version it was possible to have methane breathing races (a la Hydrans in SFB) but this hasn't been implemented yet

[Density]

http://aurora2.pentarch.org/index.php?topic=8495.msg101987#msg101987

Taking the default humans as an example (as in, no tolerances have been altered when generating the game) this is how breathable atmo works. They have an ideal Oxygen pressure of 0.2, with a max deviation of 0.1. So, any amount of Oxygen from 0.1 and 0.3 is needed. To be clear, that number is atmospheric pressure, not % of total atmosphere. You also need other gasses to lower the % that is Oxygen to 30% or lower. That 30% is an absolute set by the game, and has nothing to do with max racial tolerance. All gasses (including dangerous gasses and water vapor) work for this, but inert gasses are preferable: dangerous gasses quickly cause a CC cost at least as high as not having a breathable atmo, and water vapor will fluctuate until some time after you stop terraforming (assuming a temp range for both condensation and evaporation).

Also note, Aestusium and Frigusium are inert, meaning you can adjust for temperature and work towards getting Oxygen at/under 30% at the same time.

Of the dangerous gasses, Carbon Dioxide has the highest safe level, but even that counts as dangerous at 0.5%.

[Agraelgrimm (OP)]

Wow. Very in depth, thank you very much.