Compressors are chosen or developed according to their defined pumping duty.
The physical and chemical properties of the gas to be compressed influence the design of the compressor.
Compressors pumping dangerous media (e.g. toxic, inflammable, explosive, corrosive, radioactive, damaging the ozone layer). They have to be built in such a way that there will be no external leakages (i.e. with special external seal systems or without external moving seals as hermetic compressors).
If the media to be compressed should not come into contact with oil for reasons of safety or hygiene, the compressors will have to be of the nonlubricated design (nonlubricated compressor).
From the composition of the gas, mean values of the gas constant and isentropic exponent can be derived, see Table 2.5.