> For the complete documentation index, see [llms.txt](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/deep-seas/mechanics/oxygen.md).

# Oxygen

A sealed hull keeps the sea out, but without an oxygen system the mod treats it as a boat, and a boat that ends up underwater floods (see [Sealed hulls](/create-deep-seas-wiki/deep-seas/mechanics/sealed-hulls.md)). To dive with a dry, breathable inside, the submarine needs oxygen.

## The oxygen chain

1. **Water into the** [**Electrolyzer**](/create-deep-seas-wiki/deep-seas/air/electrolyzer.md)**.** Every tick it turns 10 mB of water into 10 mB of oxygen, for 250 FE. That is 200 mB of oxygen per second, as long as it has power, water and room in its oxygen tank.
2. **Oxygen into the** [**Oxygen Diffuser**](/create-deep-seas-wiki/deep-seas/air/oxygen-diffuser.md)**.** Pipe it over. The diffuser holds 1 bucket.
3. **A redstone signal on the diffuser.** Without it, nothing happens.

The diffuser uses **50 mB of oxygen per second** while it runs, whatever the size of the submarine. One Electrolyzer running non-stop keeps four diffusers going.

When the diffuser starts, it bubbles for 5 seconds before the air takes. After that, every sealed room of the submarine is full of air: you walk instead of swimming, you breathe, and the sea stays out.

{% hint style="warning" %}
If the diffuser runs dry, the submarine stops being a submarine. A sealed room covered by the sea for two seconds then floods. Keep the oxygen flowing.
{% endhint %}

## Powering the Electrolyzer

* **FE** from an energy mod (Create Crafts & Additions, Create New Age, Create Power Grid). It stores 10,000 FE and takes up to 1,000 FE per tick.
* **Rotation**, with a Create Shaft in its module slot. It makes 4 FE per tick for each RPM, up to 1,000 FE per tick, so 64 RPM is enough to run it non-stop. The module costs 8 SU per RPM.

## Other sources of oxygen

* The Oxygen Diffuser takes any fluid in the `#c:oxygen` tag, so oxygen from other mods works too.
* The [Oxygen Bucket](/create-deep-seas-wiki/deep-seas/air/oxygen-bucket.md) carries a bucket of oxygen by hand.
* The [Creative Oxygenator](/create-deep-seas-wiki/deep-seas/air/creative-oxygenator.md) keeps a submarine full of air with no oxygen at all, for creative builds.

## Things to know

* Only one oxygen system runs a submarine at a time. A second diffuser on the same ship is a backup: it takes over if the first one stops.
* The diffuser rescans the ship when the hull changes, and every 10 seconds otherwise.
* Ships bigger than 500,000 blocks are not filled (`oxygenMaxFillBlocks` in the server config).
* Nothing can be placed in the space right above an Oxygen Diffuser or an Electrolyzer, their model takes it.
* The air is only for breathing. It does not lift the submarine, the [ballast](/create-deep-seas-wiki/deep-seas/mechanics/diving-and-surfacing.md) does.