Skip to main content

Air Separation Module (ASM)

Generating nitrogen to protect fuel tanks against fire or explosion

The Air Separation Module (ASM) is part of the inerting system (OBIGGS: On-Board Inert Gas Generating System or NGS - Nitrogen Generating System).

The ASM consist of a hollow fiber membrane and a metal pressure shell rated for flight. The hollow fiber membrane generates nitrogen inside fuel tanks in order to reduce the oxygen level and thereby minimize the risk of explosion.


  • Patented design
  • Simple and versatile integration
  • No calibration or logistics
  • Reduced maintenance
  • Maximized ASM's operating life

How does it work?

The membrane developed by Air Liquide was designed to meet the standards of weight and reliability required by the aerospace industry for Fuel Tank Protection System (FTPS). The membrane’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.

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.

Performance and technical specifications

  • Optimized for fiber stability, distribution of gas, uniformity of input pressure, and the best division of mechanical stress
  • 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
  • Dimensions and characteristics can be tailored to your specific need

Contact Us

For more information, find on this page your key contacts and our contact form.

Contact Us


Air Liquide designs, manufactures and services gas-related equipment on board aircraft and on the ground, for civil and military markets.

Discover our solutions