Advanced Atmosphere

Lore & Background

In the layered cross-section that forms ONI's world, atmosphere is not a given; it is a resource you must manufacture, filter, and pump. The Basic Atmosphere tier gives a fledgling colony just enough O₂ and CO₂ handling to keep a handful of colonists from suffocating in the first few cycles. Advanced Atmosphere represents the next evolutionary leap: the colony has outgrown its single oxygen plant and is ready for industrial-scale gas management.

The machines unlocked here are the workhorses of any serious mid-to-late game setup. The Advanced Oxygen Plant splits water into breathable oxygen and a hydrogen byproduct, while the Advanced CO₂ Scrubber pulls carbon dioxide out of the air and vents it. Together they form a closed-loop breathing system that can sustain far more colonists, far more machinery heat, and far more agricultural activity than the basic equivalents ever could.

For players, the moment of building the first Advanced Oxygen Plant is often a small emotional beat: the colony stops being a desperate survival experiment and starts feeling like a real, self-sustaining underground civilization. The hum of the machines, the steady green O₂ readings climbing back toward safety—it is the sound of a colony that has chosen to stay.

In Their Own Story

The research station's progress bar crept past the final percentage, and a soft chime echoed through the cramped lab. Yuki stared at the newly available blueprint, the little icon of the Advanced Oxygen Plant glowing in the tech tree like a promise.

Outside the glass wall, the colony's single basic plant was already wheezing, its O₂ output barely keeping pace with the heat the smelter was dumping into the air. Three colonists had spent the last two cycles in the low-oxygen warning zone, their little avatars hunched and grey.

She queued the build. Two tiles of rock cracked away. The new machine slid into place, its water intake port already gurgling with the first split molecules. Within a single cycle the O₂ gauge, which had been pinned at a worrying 12 percent, began a slow, steady climb. Yuki exhaled—actually exhaled, a long breath she hadn't realized she'd been holding—and turned back to the smelter. The colony would breathe tonight. Tomorrow they could think about the hydroponics.

Reader's Guide

The Advanced Atmosphere tech line sits in the Life Support branch of the research tree and requires the Basic Atmosphere tier to be completed first. Research is generated by having one or more Research Stations powered and staffed.

Key blueprints unlocked (general descriptions; exact research costs vary with game version and patches):

Advanced Oxygen Plant — Splits water into O₂ and a hydrogen byproduct. Higher throughput than the basic plant, making it the backbone of mid-to-late game oxygen supply. Requires a water input and a power connection.

Advanced CO₂ Scrubber — Removes carbon dioxide from the local atmosphere at an increased rate. Pairs naturally with the Advanced Oxygen Plant to form a complete gas-exchange loop.

O₂ / CO₂ Pump (if included in this tier) — Actively moves oxygen or carbon dioxide between sealed areas, letting you route breathable air to distant labs or vent CO₂ into a dedicated storage pocket.

Practical tip: place Advanced Oxygen Plants near a reliable water source (a water pump or a nearby water pocket) and keep a small buffer of water so the plant never starves. Pair each plant with at least one Advanced CO₂ Scrubber in the same sealed zone to prevent CO₂ buildup from choking your colonists. Monitor hydrogen byproduct levels; vent it to a safe pocket or use it as fuel in a hydrogen burner to avoid a toxic gas pocket forming around the plant.

Did You Know?

• The Advanced Oxygen Plant produces hydrogen as a byproduct of splitting water, meaning every unit of O₂ you generate also creates a flammable gas you must manage or repurpose.
• In ONI's cross-section, gas behaves with real buoyancy: O₂ and other lighter gases rise while CO₂ and heavier pollutants sink, so the vertical placement of your scrubbers and plants actually affects how efficiently the r
• The shift from basic to advanced atmosphere machines is often the single biggest quality-of-life upgrade in a colony's early-to-mid game, reducing the number of individual machines a player must build and maintain.
• Oxygen Not Included's 2D cross-section art style was designed to make the player feel like they are looking at a geological slice, and the atmosphere tech machines are deliberately rendered as chunky, industrial units to