During the past years a growing number of scientists and engineers have investigated ionic liquids because of their outstanding advantages in several areas. Their unique physical properties and specific chemical behavior make these liquids very interesting for new and innovative applications. For commercial implementation ionic liquids have to meet a number of requirements. For use in high pressure applications they should have a low compressibility, an adjustable gas solubility and a superior lubricating ability. A screening of the relevant parameters was conducted in several experimental setups built for these purposes. Most of these parameters were also examined under long term conditions with regard to real process conditions and safety guarantee in possible high pressure applications. A major application is the compression of oxygen using ionic liquid as operating fluid. Besides, there are many more applications where the superior chemical and physical properties of ionic liquids are of high potential benefit.