From Unofficial Stationeers Wiki
Carbon dioxide (CO2) is a non-flammable gas found in some atmospheres naturally (such as Mars). It can also be produced by burning Fuel or Coal, smelting most ores (e.g. Iron, Copper, and Silicon) and through human respiration. It is required in any amount for plants to grow; higher amounts of CO2 will cause them to generate Oxygen.
Carbon dioxide has a specific heat of 28,2 Joule / mol.