The cryogenic air separation technology is used since more than 100 years for production of oxygen, nitrogen and argon. The modern trends in the air separation are discussed in the present paper. One of them is, that the specific cost of the system becomes more important during the optimization last time. The high availability and reliability is a further significant optimization parameter, while the power consumption is secondary parameter only often. Therefore the use of internal compression for oxygen pressurisation instead of the more dangerous and expensive oxygen compressors becomes more popular. Some basic principles for conceptual design of modern air separation plants made by «Linde» are described in this paper. According to this concept the packed columns are used for production of argon as well as purification units based on molecular sieve adsorption without refrigerators. The whole low-temperature part of the air separation plant is made from aluminium. An further essential issue is that the company «The Linde Group» is able to manufacture all kind of key equipment for low temperature systems.