In Oxygen Not Included, what parameters are important when using a gas or liquid, pumped in a loop between the area you're trying to cool and the area you're trying to dump the heat (e.g. the cold biome)? Are some fluids unambiguously better for this task than others?

I've seen several youtubers say that hydrogen is good for cooling - is that accurate, and if so what is the math behind it? Hydrogen's low specific heat capacity means that when you pipe it through the cold area, it gets much cooler than, say, oxygen. But I would expect that the effect is symmetric, and even though the hydrogen is colder when it gets to your base, it will also warm up faster and thus will not remove any more heat than if you used oxygen.

I've also seen oil used as the cooling medium. The wiki mentions that oil did not used to be freezable so it was used as a cooling medium, but now that it has a freezing point, does it provide any advantage over, say, water?

  • Just realized there may be a different answer between passive cooling (run gas through the cold biome) and active cooling (thermoregulator).
    – Selvek
    Jan 9, 2018 at 0:41

1 Answer 1


Hydrogen has one of the highest Specific Heat Capacities for a gas.

Heat capacity of gas I think this table is up-to-date, listing hydrogen with the highest SHC at 2.4, and a higher thermal conductivity, meaning it can exchange heat faster.

If you want to use liquids, check out this one: Head capacity of liquid

However, I believe polluted water will have the same SHC as water in the next patch (rocketry). Polluted water may still be your best bet with high SHC and lower freezing point.

The high SHC of hydrogen is also useful for cooling with wheezeworts, as they cool a gas a certain number of degrees, so hydrogen will get more effective J of cooling per puff.

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