Basic Atmosphere

Lore & Background

In the world of Oxygen Not Included, the duplicants are synthetic lifeforms designed to build and maintain a colony deep beneath the surface of an unknown planet. They breathe, they eat, they feel, and they die without oxygen. The planet's atmosphere, where it exists at all, is not immediately hospitable, and the subterranean layers where the colony operates are sealed, stagnant, and slowly filling with the CO2 the duplicants exhale with every breath.

Basic Atmosphere is not a grand invention. It is the first practical answer to the question "how do we not suffocate?" The O2 Generator it unlocks is a modest, boxy machine that sits at the intersection of three resource streams: it ingests carbon dioxide, it ingests water, and it outputs oxygen. It is powered, it is simple, and it is the single most important machine in the entire colony for the first several in-game days. Every other system—growing crops, running research, expanding into new biomes—presupposes that the duplicants are still breathing.

Fans of the game often describe the early atmosphere management as the true tutorial: learning to balance CO2 intake, water supply, and power draw around a single O2 Generator is the moment the colony simulation clicks into place. It is where the player first feels the weight of a closed system, where every molecule matters, and where the elegant interlocking of ONI's resource loops becomes visible for the first time.

In Their Own Story

The duplicant crouched beside the O2 Generator, watching the small gauge flicker. Three days into the colony, the CO2 readings in the main habitation room had crept past the comfort threshold, and two of the crew had already complained of headaches. She pressed her palm against the warm casing of the machine and felt the faint shudder of its internal cycling—CO2 in, water in, O2 out. The water tank was at forty percent. She had exactly enough for another two days if she rationed.

Above, the rock groaned with the slow patience of geology. Below, the colony hummed its small, desperate hum. She pulled up the schematic on her wrist display, traced the pipe routes, and made a quiet decision: tomorrow, they would dig for water. Tonight, the generator would keep breathing for all of them.

Reader's Guide

Basic Atmosphere is a Tier 1 technology in the Atmosphere / Life Support branch of the research tree. It requires no prior techs and is one of the first entries available to a new colony.

**Unlocks: O2 Generator** - Function: Consumes CO2 (gas) and Water (liquid) as inputs and produces O2 (gas) as output. Requires a continuous power supply to operate. - Role in colony: The primary source of breathable oxygen for duplicants. Without it, the colony will suffocate within a few in-game days as exhaled CO2 accumulates in sealed rooms. - Key consideration: The O2 Generator needs a steady supply of both CO2 and water. CO2 is produced passively by duplicant respiration, but water must be sourced from the environment (aquifer drilling, rain collection, or later, desalination). Power draw must be budgeted alongside other early machines.

**Practical tips for early play:** - Place the O2 Generator in a room that receives CO2 from the main living area (duplicants exhale into the shared atmosphere). - Ensure the water input pipe is connected to a water source before the CO2 runs out—running dry on water stops O2 production entirely. - Pair with an O2 Tank (if available at this tier) to buffer output and prevent momentary oxygen dips during power interruptions. - Keep the generator's exhaust (if any) vented to a CO2 collection area to avoid contaminating the O2 output stream.

This single tech is the gateway to the entire atmosphere management loop in ONI. Master it, and the colony breathes. Neglect it, and the lights go out in the most literal sense.

Did You Know?

• The O2 Generator is the only machine in the early game that actively *creates* breathable oxygen from other resources; every other O2 source is either storage or a later-tier conversion.
• In ONI's closed-system design, the CO2 the O2 Generator consumes is the same CO2 the duplicants exhale—creating a self-sustaining loop that is the core elegance of the game's atmosphere management.
• If a colony's power supply drops while the O2 Generator is running, it stops producing oxygen immediately, which is why early players are taught to keep a small battery or backup generator dedicated to life-support machi
• The O2 Generator's water requirement means that a colony with no water access cannot sustain its atmosphere indefinitely, linking the atmosphere system directly to the water and drilling tech trees from day one.