Air

Past the wall the air is sour gas — hydrogen sulphide out of the deep ground and the smoke of gas fires — and a roof does not answer it. The short version is on the Dark Zone page on the site.

The dose

While you breathe sour gas, a dose builds in you — faster the deeper you are, faster still while you fly. Past a point it poisons you, harder as it climbs.

The sign right of your hotbar shows where you stand: bare, the dose you have taken; behind a mask, the time left before the worst of it; on a tank, the air left. Deeper in it carries more pips as the air you set out with is spent.

The mask and filters

A mask with a filter slows how fast the dose builds and burns the filter as you breathe. Filters burn out — carry spares.

The deeper you go, the better the filter you need: pale, yellow, black. A filter is made from the sulphurbloom flower, and the deeper it ripened, the darker it is.

A Create backtank worn with a diving helmet stops the dose until its air runs out.

Tainted food

Food caught or killed past the wall outside a sealed room is tainted. A furnace, smoker or campfire does not clean it, and eating it is a dose of its own, out there or at home.

The sealed room and the scrubber

Only a sealed room served by a scrubber is clean air.

• A scrubber turns on Create rotation and burns filters. It needs a better filter the deeper it stands, as a mask does, and in the deepest layers it burns fuel as well. Which filter, and where fuel is needed, is in the layer table on the Dark Zone page.
• The room must be closed on every side: an open door is a leak. A faster shaft holds a bigger room.
• A scrubber serves a room that stands still; carried on a moving contraption, it serves nothing.
• Goggles on a scrubber say whether its room is sealed, and why not.
• An air gauge set into the room gives a comparator the reserve, which is what an airlock needs. A comparator on the scrubber itself reads the whole hours of air the room has left, so a train can be sent before it runs dry.
• A depot board set beside a scrubber shows, through goggles, the room's air, its fuel, the breathing stored in its backtanks and what draws on its shaft.

When a seal breaks the room lives on its reserve for a while — nothing pulls you towards the gap — and then it is open air.

Inside, the dose falls and nothing hostile rises: Tlin, which walks the dead, cannot live in clean air. A bed there is somewhere to come back to.

What grows past the wall

Ordinary life does not grow in sour gas. Outside a sealed room, crops stand still without dying, animals will not breed, and a beast left there breathes the air as you do. A sealed room is your greenhouse and your barn.

Sulphurbloom is the other way round: it grows only past the wall and outside clean air, and at home or inside a sealed room it wilts — it never dies, and taken back out of clean air it ripens again. Its seeds come from the zone's own vents, from caches and from some of the dead.

So the thing that keeps a base breathing grows outside that base — which is why people build out there, and why they build together.