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air separation module


Protecting fuel tanks against the risk of explosion

The ASM (Air Separation Module) is the part of the inerting system (OBIGGS or NGS) that generates nitrogen inside fuel tanks in order to reduce the oxygen level and thereby minimize the risk of explosion.

air separation module
Air Separation Module

Air Separation Module

The membrane developed by Air Liquide was designed to meet the standards of weight and reliability required by the aerospace industry. The ASM’s permeability depends directly on the surrounding pressure and temperature.

As part of an OBBIGS, the membrane produces nitrogen from the air surrounding the aircraft. It is made up of tens of thousands of hollow polymer fibers that have roughly the same diameter as a strand of hair. When air goes into the membrane, it flows into the hollow fibers. While oxygen can cross the walls of these fibers and is evacuated, the nitrogen goes along the length of the fibers. At the end of the process, only 99%-pure nitrogen is left. The nitrogen is then sent into the tanks in order to replace the oxygen and thereby limit the risks of the fuel igniting, thereby helping to protect the safety of the crew and the passengers.

Expertise based on millions of hours of flight time

The Group has been developing membranes since 1989 for multiple applications, including aerospace, pharmaceuticals, chemistry, and electronics. Air Liquide was a pioneer in the use of permeable membranes on commercial aircraft, working with the FAA (Federal Aviation Administration) to improve the safety of fuel systems as early as 1996, following the incident involving TWA flight 800.

Millions of hours of experience have enabled Air Liquide to develop extremely high-performance polymer fibers that provide the best possible solution for its customers. The design and production of the fibers is optimized to improve productivity and obtain the highest level of nitrogen purity.

A patented system

The mechanical integration of the membrane in an envelope is a patented design. It optimizes fiber stability, the distribution of gas, the uniformity of input pressure, and the best division of mechanical stress, in order to maximize the ASM's operating life.


  • Maximum operating pressure: 60 psig
  • Operating temperature : 160°F +/- 10°F
  • Ambient temperature range : -67°F to +185°F (-55°C to +85°C)
  • flow rate : between 0.5 lb/min and 3.5 lb/min
  • NEA purity: between 1% and 10% O2 content
  • max weight : < 12kg
  • overall dimensions : D 260mm x L 965mm

Key benefits

  • Simple and versatile integration
  • No calibration or logistics
  • Reduced maintenance


  • Boeing 737 NG civil aircraft
  • Boeing MC-21 civil aircraft

Discover also



Oxygen analyzer

As part of an OBIGGS , the oxygen analyzer ensures that the system is in good working order. It analyzes the oxygen-depleted gas and sends an electrical signal reflecting the quantity of oxygen as a percentage or in partial pressure. The O2 analyzer is fitted with a zirconium oxide sensor to ensure its precision and reliability. It can operate at a wide range of pressures, from a few millibars to several bars and temperatures of up to 300°C.