Carbon Dioxide

Carbon Dioxide is a common gas in Oxygen Not Included and one of the most important early byproducts to manage. It is heavier than most breathable gases, so it naturally sinks and pools in low areas, pits, and the bottoms of funnel-shaped spaces. This makes it easy to collect deliberately, and it also makes it a frequent problem in early bases as Duplicants, generators, and industry steadily produce more of it.

In-game, Carbon Dioxide is treated as a sterile environment. Food stored in it rots more slowly, and if the food is also kept deeply frozen it will not spoil at all. Because it is common and naturally settles downward, Carbon Dioxide is often used as a simple food-storage atmosphere or as part of a “carbon pit” where unwanted gas is allowed to accumulate until it can be skimmed, compressed, vented to space, or otherwise processed. It does not interfere with Compost, and it is safe for plants.

Carbon Dioxide is also a useful growth and creature resource. Dusk Caps and Oxyferns require a Carbon Dioxide atmosphere to grow. Slicksters consume Carbon Dioxide and excrete Crude Oil, while Molten Slicksters consume it and excrete Petroleum. Beeta also consume Carbon Dioxide; when they do, they fall asleep and cannot sting Duplicants, and a sleeping Beeta produces radiation.

A number of buildings and systems either create or consume Carbon Dioxide:

• Duplicants exhale Carbon Dioxide continuously.
• Coal Generators, Natural Gas Generators, Wood Burners, and Petroleum Generators all output it as a by-product.
• Polymer Presses, Gas Ranges, and Ethanol Distillers also produce it.
• Carbon Skimmers remove it from the air by turning Water into Polluted Water.
• Algae Terrariums can capture it into Polluted Water while consuming Water.
• Soda Fountains consume Carbon Dioxide along with Water and provide Morale and Science.

Carbon Dioxide can also appear from geothermal and world generation sources. Carbon Dioxide Vents produce hot gas that is too warm for Slicksters, while Liquid Carbon Dioxide Geysers output much colder Carbon Dioxide that is easier to use directly and can help cool industrial areas. Some rocket engines and solid fuel thrusters also exhaust superheated Carbon Dioxide, and Meteor Showers can bring additional amounts. It can even be harvested on certain space missions from renewable space points of interest.

If cooled below its condensation point, Carbon Dioxide can be stored safely as either a liquid or a solid. That makes it useful for compact storage and for specialized cooling setups. In practice, players often exploit its tendency to pool, its sterile nature, and its role in creature and plant ecology to turn what begins as waste into a useful resource. One caveat is that the game includes liquid Carbon Dioxide even though real Carbon Dioxide normally bypasses the liquid phase under standard atmospheric conditions.