I found this statement on some Starbound Wiki:
Another way around this is to dig downwards from spawn and find an underground tunnel. This tunnel will most likely hold oxygen, but be sure to close it up behind you, else all of the oxygen will escape into space and leave you no better than where you started.
This sounds really cool; the concept of air actually being inside caverns and leaking out, provided that that quotation is even correct, which I couldn't verify.
My question is, can you create a room filled with air? I have some airlock door schematics, maybe they're for that purpose?
Best Answer
That wiki is out of date, you should be using Starbounder, which is the official wiki.
There is no air on moons, period. If you don't have a Breathing EPP, you will start to lose air as soon as you teleport down to the the moon (same for asteroid fields).
The airlock door schematic you've found is just a "recipe" to craft a door that happens to have the name "airlock door". It functions like any other door (though it is a bit larger than usual). Any door type can be used for an actual airlock structure (which are really only functionally useful for clearing liquids in, for example, an ocean base).
[On a side note, I played Starbound since the the beta was released and I don't remember any air escaping mechanics described in your wiki entry ever being in game, though it's been a while so maybe I don't remember correctly.]