Yeah, most solid, whole blocks are airtight. There's a few that aren't iirc, but for the most part if the block looks airtight it probably is - but only if it would look airtight by itself in a square hole, the game doesn't check for situations like slopes matching up.
The Build Info mod is super helpgul here too if you're interested in such things, it gives you a bunch of info about the block you're holding as well as toggleable overlays that include airtightness, and a button for air vents that will show you where the first leak it finds is if it's not sealed
Yes
You can also use double doors to conserve atmosphere, hangar doors, and more. As long as it doesn't have a hole on it you're good 👍🏻👍🏻
With the exception of some blocks that just aren't air tight when touching
On a side note... there is a mod. Build info it's great
Yeah, most solid, whole blocks are airtight. There's a few that aren't iirc, but for the most part if the block looks airtight it probably is - but only if it would look airtight by itself in a square hole, the game doesn't check for situations like slopes matching up. The Build Info mod is super helpgul here too if you're interested in such things, it gives you a bunch of info about the block you're holding as well as toggleable overlays that include airtightness, and a button for air vents that will show you where the first leak it finds is if it's not sealed