Cooling medium comprising an ionic liquid with a hydrogen content of 0% to 8.5% by weight. The cooling medium can be used in a method for cooling a technical device, examples of which include: metallurgical ovens and their aggregates, ovens and aggregates in the glass and ceramic producing industry, ovens and aggregates in the cement producing industry, reactors and aggregates in gasification of organic matter and biofeedstocks, ovens and aggregates in incineration plants, reactors and aggregates in nuclear power plants, and combustion chambers and aggregates in conventional thermal power plants.