Gunk

Gunk is a liquid element in Oxygen Not Included. Like other liquids, it is affected by gravity, can flow across level floors and through open doors, and will settle into layers when mixed with other liquids of different densities. It can be moved through liquid pipes, but pipe contents that change phase can damage the pipe, and liquids in tiles can also cause pressure damage if they build up too much mass.

In general, Gunk follows the standard liquid rules: it cannot exist in amounts smaller than 10 g outside of pipes, it will be destroyed if exposed to space unless protected, and it can contribute to submerged Duplicants drowning or burning if the liquid is hot enough. Its physical behavior is therefore mostly relevant for storage, transport, and pressure management rather than for any special movement or interaction of its own.

One practical use for Gunk is as a crafting ingredient in a conversion that consumes 80 kg of Gunk plus 200 kg of another input to produce 1 unit of the output product. Using that product increases a Duplicant’s internal gear-oil amount by 80 kg. This makes Gunk a resource with a direct role in that production chain rather than merely a waste liquid.

Because it is a liquid, Gunk can also be handled with the same infrastructure used for other fluids:

• It can be stored in reservoirs and transported through liquid pipes.
• It will obey liquid layering rules if combined with other fluids.
• It can create pressure against tiles when packed too densely, so containment strength still matters.
• If heated or cooled past its phase-change limits, it will behave like any other liquid and may transform accordingly if the conditions are met.

Gunk is therefore best treated as a specialized liquid resource with at least one notable downstream crafting use, while otherwise following ordinary liquid physics.