Carbon freezing chambers are used for the process of storing Tibanna gas in carbonite to preserve it while it is being transported over long distances. A number of such chambers are constantly in use in Bespin's Cloud City.
In the freezing process, the gas is pumped into the chamber where it is mixed with molten carbonite, then flash-frozen to cool the carbonite into a solid block. The gas is released later at its destination or at a processing center. But the chamber might have other, unintended uses.