question about expandiing the hull

"Ah excellent.  Will oxygen fill the new area once it is completed, or do I need to put an O2 generator in first?"

Oxygen will flow into the new area, the doors have vents in them that allow gases to pass through, you can also add air vents to the walls so a new O2 generator isn't necessary but do keep an eye on it, larger builds may need additional O2 generators to compensate.

Also remember temperature regulators, the walls are insulators so not as much heat passes through to new rooms.

"Smoke me a kipper, I'll be back for breakfast"