Making oxygen in Oxygen Not Included isn’t really that complicated but you’ll soon realise that you can’t just depend on algae forever. Perhaps the hardest wall to get past in the game for new players is generating oxygen in a way that’s sustainable in the long run. This is because both of the early game oxygen generation methods depend on a constant supply of Algae. Oxylite helps you get through the starting phases of the game but it quickly runs out. It was never supposed to be a permanent oxygen source.

After getting through your first couple of cycles and setting up an outhouse, your next aim should definitely be to quickly figure out how you’ll be generating oxygen for the colony. Remember that gases in Oxygen Not Included do have their own densities, so hydrogen will always rise and carbon dioxide will fall to the bottom of your base. Similarly, oxygen is lighter than carbon dioxide so it will rise as well. Keeping this in mind, your oxygen production should be at the bottom of your base.

The different methods of producing oxygen

To list them in no particular order:

  • Oxygen Diffuser
  • Algae Terrarium
  • Deodorizer (Filters polluted oxygen)
  • Electrolyzer (The ultimate solution)

Before we begin, let’s go through some facts. There are multiple ways to lose your colony in Oxygen Not Included. Running out of water is just as threatening as a lack of breathable oxygen. This is because water is a key ingredient in most food recipes and until you can get to a sustainable source of food, mixing water with dirt is your only way of feeding your duplicants. While we’re on the topic, you really shouldn’t using water for food in the first place.

Each duplicant requires 100g/s of oxygen.

  • Most water outside of the starting area is going to be polluted.
  • Consuming food made with polluted water will cause food poisoning.
  • It is in our best interest to make sure that we use our starting water reserves as slowly as possible.

Let’s begin then.

Oxygen Diffuser – is it worth it?

Oxygen Diffuser
Oxygen Diffuser

The Oxygen Diffuser consumes algae and outputs a significant amount of oxygen (500g/s).

However, it requires power to covert the algae into oxygen. 120W of power is a lot to ask for in the early game but a single Oxygen Diffuser can potentially generate enough oxygen for up to five duplicant. That is, as long as it’s placed in the right spot. Remember that Oxygen won’t rise as fast in tight spaces so you should always leave enough room between your rooms.

Oxygen Diffusers will quickly burn through your algae reserves if left unchecked. Outside of your starting area though, algae is very hard to come by. Converting slime into algae for oxygen production isn’t unheard of, but even that can’t be sustained permanently. Sooner or later you’ll be running out of slime as well. It’s a much better idea to rip off the band-aid as soon as possible.


Algae Terrarium
Algae Terrarium

The Algae Terrarium is a noob trap which you should avoid at all costs. Keep on reading if you wish to know why. They do give a better algae to oxygen ratio but that’s where the comparison should end.

It doesn’t require any power to function, gets rid of carbon dioxide, seems like the perfect solution to all our oxygen problems, right?


The Terrarium uses a shocking 300g/s of water. Remember how we talked about the importance of water in the early game? The terrarium will quickly use up your starting reserves of water.

You need 2.5 terrariums for each dupe in your colony. So compared to the Oxygen Diffuser you’ll need 13 algae terrariums to sustain five dupes, since we can’t build half a terrarium.

These thirteen terrariums will be consuming 3.9 kg of water per second.

That’s 2,340 kg of water per cycle, which could’ve been used to make 31 mush bars. Every. Cycle.

Simply avoiding the algae terrariums would make your colony last a lot longer. You’re welcome.


Oxygen Deodorizer
Oxygen Deodorizer


Putting these near your polluted oxygen generators and polluted water reservoirs is an excellent idea to avoid any polluted oxygen pockets in your base. They’re able to catch polluted oxygen in a 5×5 area around them but not through tiles and doors. We’d also recommend them to be placed near Composts and Algae Distillers.

Placing them in swamp biomes is an even better idea. Slimelung germs can’t survive outside of polluted oxygen, so it is a common strategy to slowly convert the polluted oxygen being produced in swamp biomes into a much more cleaner, breathable, oxygen which can then be pumped back to your main base. Just make sure it wasn’t contaminated by slimelung before pumping it back.


Oxygen Electrolyzer
Oxygen Electrolyzer

This is where things start getting a lot more complicated. Producing oxygen is no longer about putting in one material and getting another in return. If you’ve familiar with high school chemistry then electrolysis shouldn’t be a stranger to you. The Electrolyzer in Oxygen Not Included works similarly. We break up water into its components, oxygen and hydrogen.

Unfortunately for colony building purposes, the hydrogen isn’t really helpful. It clusters together, forms pockets and is a pain to get rid of.

This is where our friendly gas filter comes in. A basic Electrolyzer process for oxygen generation requires a small, sealed room with the Electrolyzer itself in it. A pump which collects the gases in that room and sends them through a gas filter. Oxygen is circulated around your base while the hydrogen is sent off to a hydrogen generator where it’s quickly used to produde power.

What’s the catch you ask? Water. You’ll need a lot of water in the long run. Having a steam geyser or two wouldn’t hurt at all. That is, so long as you’re well equipped to deal with the added heat.


Electrolysis is by far the best method to keep your duplicants breathing but it takes a lot of effort to properly set up. It doesn’t require any algae but the water requirements will challenging for new players. Thankfully water stops being a problem once you’re later into the game and have access to a steam geyser, water purification and find out the magical secret to infinite water.

What we’re trying to say is that there’s no best way of generating oxygen from the get-go. You’ll be switching between a couple different methods while adding in a carbon skimmer eventually.


Oxylite should be everything you need for your first few cycles. Try to set up basic power generation as soon as you’re done making an outhouse because oxylite doesn’t last forever and the oxygen diffuser should be your go-to method of producing oxygen.

Since oxygen tends to rise, the oxygen diffuser will only be able to support the areas above it. So it’s a good idea to keep it near the bottom. Try to avoid large pockets of vacuum for now since you’ll need to fill all of that area with gases. The only gases you’ll be making early game are form the oxygen diffusers themselves. Algae is very easy to burn through.

Algae Terrariums on the other hand should not be considered at all. Not only do they require a ton of water, they also require your duplicants to supply that water. That’s time that your duplicants could have spent elsewhere. Besides, the amount of carbon dioxide they remove from the air isn’t really worth the amount of water you spend.


This is when carbon dioxide becomes a problem

By now you’ve probably ran out of all the oxylite, you’re beginning to actually look for algae deposits and the bottom of your base has become a pit filled with carbon dioxide. This is also the time when you should be aiming towards a more permanent solution for your oxygen problems, hopefully one that doesn’t depend on resources being supplied manually.

Having pits of carbon dioxide doesn’t depend on which oxygen production method you use. No matter what you do, you’re always going to have to deal with it. The best way of doing so is by using a carbon skimmer. It uses clean water to remove carbon dioxide from the air and produces an equal amount of polluted water. The water is only consumed when the skimmer is actively cleaning carbon dioxide. It’s a good idea to have everything important in your base be above the skimmer itself. Everything a couple tiles below it will fill up with carbon dioxide, so have your mushroom farms over there.


This is when an electrolyzer needs to be used – you’ll never worry about oxygen production ever again.

Unless you’re attempting to build an SPOM, a self-powered oxygen module, it doesn’t even need to be that complicated. Start with a small room, have an electrolyzer inside and a pump. Take the pump’s output through a gas filter and filter out hydrogen. Send the hydrogen off to a hydrogen generator and the oxygen to wherever it’s needed.

Unfortunately, the output temperature for the electrolyzer’s gases is very high. So using wheezewort plants from the cold biome to cool things down should be a priority. There are numerous other methods of cooling stuff down as well but wheezeworts are far superior for oxygen generation.

And while you’re at it, why not build an SPOM from the get-go? You’re gonna want one eventually.


  • Was there an update that changed something we talked about?
  • Did we forget to talk about something?
  • Are we wrong about something?

Let us know in the comments!