ASU package is like a huge and extremely precise "air filter + distiller". The air mainly consists of nitrogen (N₂, approximately 78%), oxygen (O₂, approximately 21%), argon (Ar, approximately 0.93%), as well as small amounts of carbon dioxide, neon, helium, krypton, xenon and other rare gases, and water vapor. The core task of the air separation unit is to separate the air and produce high-purity gases such as oxygen, nitrogen, and argon. Sometimes, rare gases are also extracted.The main principle of air separation is to use physical methods (mainly deep freezing and distillation) to "break down" the air into high-purity industrial gases such as oxygen, nitrogen, and argon. These industrial gases are the indispensable "industrial blood" and "industrial food" for modern industry, supporting steel metallurgy, petrochemicals and coal chemical industries, electronics and semiconductors, mechanical manufacturing and metal processing, medical and health care, food and beverages (nitrogen packaging and preservation), aerospace, water treatment and environmental protection, and other various industries.