Air Separation Unit (ASU): How Air Liquide produces gases essential to industry and healthcare

Published on March 12, 2026

2 minutes

The manufacture of many everyday products, from smartphones to medical devices, relies on essential industrial processes that include the separation of gases from air. Using the cryogenic process at the heart of an ASU (Air Separation Unit), Air Liquide separates air into different gases (oxygen, nitrogen, argon) on an industrial scale. Discover how this technology works in video.

What is an ASU?

The air we breathe is a mixture mainly composed of:

  • nitrogen (N₂): 78%
  • oxygen (O₂): 21%
  • argon (Ar) : 1 %

An ASU is an industrial facility that uses a cryogenic process to separate atmospheric air into its various main components. The aim is to produce large quantities of purified gas to meet the needs of strategic sectors such as healthcare, semiconductors, and metallurgy.

Cryogenic distillation, the fundamental principle behind ASUs

The operating principle of an ASU is based on gas physics: each gas has its own liquefaction temperature. By cooling the air to extremely low temperatures, the gases gradually change from a gaseous state to a liquid state, each at a specific threshold:

  • Oxygen: -183°C
  • Argon: -186°C
  • Nitrogen: -196°C

It is this difference in temperature that allows each molecule to be isolated by distillation.

Discover how it works in this video.

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Thanks to its expertise in cryogenics and air separation, Air Liquide thus plays a key role in many industrial and medical applications.