The Complete Beginner's Completely Incomplete Guide to Oxygen Not Included
ATMO SUIT BASICS
Atmo Suits allow your dupes to breath regardless of the atmosphere, as well as protect them from germs, debuffs from gases, and extreme temperatures.
Before you head into the oil biome, you will want to suit up. Most, if not all, of the oil biome will be so hot that it will scald your dupes.
If you are going to spend any meaningful amount of time on the surface of the asteroid, you will want to suit up. In the base game an atmo suit works well for areas with space exposure. Spaced Out adds radiation, so there a Lead Suit is a better option when heading to the surface.
Atmo suits are unlocked through research (in the Exosuits research branch).
Atmo suits are crafted using the Exosuit Forge (found under Stations).
Atmo Suit Dock
Atmo Suit Checkpoint
Crafting an atmo suit requires Refined Metal and Reed Fiber.
You can refine metal using the Rock Crusher.
Reed Fiber is harvested from Thimble Reed (found in the slime biome) or by shearing a (white) Drecko. (The blue Dreckos, aka Glossy Dreckos, give plastic instead of Reed Fiber when sheared.)
In addition to an atmo suit, you will need two buildings: an Atmo Suit Dock and an Atmo Suit Checkpoint (both found under Stations).
Without an atmo suit checkpoint, dupes won't stop to put on (or take off) an atmo suit when they pass an atmo suit dock.
To get a dupe to deliver a suit to a dock, click on the dock and select Deliver Suit.
The atmo suit dock is where the atmo suit is stored and where it fills its oxygen tank. The atmo suit dock needs to be supplied with both power and oxygen.
(As an aside, Lead Suits function like atmo suits. They use docks and checkpoints. They need power and oxygen. They are unlocked through research and built in the exosuit forge. Lead suits require lead and glass to build.)
Let's take a look at a very simple setup.
This example has only one atmo suit dock, but you can have as many as you want. Place them all next to one another, with no spaces in-between.
The green bar in the lower part of the dock shows how much oxygen it has stored.
Atmo suit docks will take damage from being pumped the wrong gas, so consider using a gas filter.
The atmo suit dock needs power or it won't fill the suit (or itself) with oxygen.
Atmo suit checkpoints have a "Clearance" setting. (Click on the atmo suit checkpoint to see it.) It has two options: "Vacancy" and "Always."
When set to Vacancy a dupe will only be allowed out if there is a free atmo suit dock for them to store the suit in.
When set to Always they will always be allowed to exit. If there are no free atmo suit docks, they will drop the atmo suit on the gound as they exit.
If a dupe has an accident while in a suit, the polluted water will stay in the suit until they take it off. When they take off the suit, the polluted water will pour out on the tile with the atmo suit checkpoint.
Atmo suits will wear out over time and become unusable. You can fix them up again in the exosuit forge. This will require reed fiber. (Click on the exosuit forge and you can set worn atmo suits to always be turned into atmo suits.)