Editing Guide to Atmospherics (section)

===Optimizing Internals===
* On a basic view, a 16 kPa minimum O2 requirement in internals. Pure O2 is theoretically toxic in real life, but has no representation for this in code, and takes a while to be really dangerous anyway (they use it to treat certain diseases, for example), and thus using a tank filled with air for internals is fairly inefficient.
* Cold O2 has more moles per kPa, and because people breathe in moles, and filling tanks usefully for internals are largely capped by the 1000 kPa release pressure, means cooling your O2 before using it in internals is important! Cooled down O2, such as from a freezer-ed canister, is the most efficient way to set up internals. Cooling it below 264 K will result in icicles inside in your lungs, though!
* If you need to empty an internal tank to make space for better, colder O2, you can use an Air Pump. Set it to ''"pump in"'' and ''"turn on"'' then ''"off"'' with the tank inside it, making it completely empty, thus allowing you to refill the tank more effectively.
* An emergency oxygen tank with normal settings lasts for about 12 minutes. Same tank, but with optimized gas temperature and output settings reduced, lasts about 50 minutes. If you don't have resources to get cooled O2 right now, set your output pressure to 16 kPa, it will give you 31 % more time to breathe.