How Do You Generate Pure
Nitrogen and Oxygen on-site?

When it comes to industrial generators, there are two primary methods for on-site nitrogen generation and one method for on-site oxygen generation – membrane technology and pressure swing adsorption (PSA). While both methods have their merits, membrane technology has emerged as the more popular choice for on-site nitrogen applications. At On Site Gas Systems, we utilise both technologies, so in each case we assess your individual circumstances and make a recommendation as to which option is right for your business.

Let’s explore the main difference between these technologies and why nitrogen membrane is a preferred in Australia.

PSA Vs. Membrane Technology - HOW IT WORKS
Pressure Swing Adsorption (PSA) Technology:

PSA systems, employ compressed air to pressurise a vessel containing carbon or zeolite materials. These materials separate gas molecules based on their physical composition or structure. When air is forced into the vessel, either N2 or O2 molecules are selectively trapped, while the other gas is released. By releasing the pressure, the captured O2 or N2 molecules are collected in a storage tank. Any unwanted gases are immediately vented into the air through a pressure release valve, where they combine back to ambient percentages. Our systems utilise two sieve beds that operate in opposing cycles, ensuring a consistent flow of the desired gas.


On the other hand, membrane technology utilises a series of hollow fibres with microscopic holes in their walls. These holes are small enough to allow O2 molecules to escape under pressure, while larger N2 molecules are unable to pass through. By directing air through the fibres, the smaller O2 molecules permeate the membrane, while the N2 molecules are captured. Heating the air within the membrane enhances molecular excitation and increases the likelihood of permeation through the holes.

PSA System Layouts for on-site Nitrogen and oxygen generation

the advantage of Pressure Swing Adsorption

In summary, PSA technology is more popular than membrane technology in gas generation due to its ability to achieve higher purity levels, its versatility in handling different feed gas compositions, and its suitability for applications that require ultra-high purity gases. However, the choice between PSA and membrane technology ultimately depends on specific requirements, purity levels needed, and the overall cost-effectiveness of the gas generation system.

why is Membrane the more popular choice

Membrane technology has gained significant popularity in recent years, particularly in industries such as oil & gas and coal mining. One of the key reasons for its widespread adoption is its inherent simplicity and cost-effectiveness. Membrane systems require fewer complex components and have lower capital costs compared to PSA technology. They offer a streamlined and efficient process for generating nitrogen and oxygen on-site, making them an attractive choice for applications where ultra-high purity is not a critical requirement. 

Additionally, membrane technology provides continuous gas flow without the need for cycle time variations, resulting in steady and reliable gas production. The ease of operation and maintenance, combined with lower energy consumption, contribute to its appeal for industrial applications. As a result, membrane technology has emerged as the go-to option in sectors where cost efficiency, ease of use, and reliable gas generation are the primary considerations.


The holes of the CMS are so small that the oxygen molecules are able to go through and get captured inside the particles, while the larger nitrogen molecules remain outside. After allowing this separation process to go on for sometime, the free floating nitrogen molecules are released out of the vessel at low pressure and captured in a storage tank. When the nitrogen has been drawn out of the tank (or sieve bed), the pressure in it is released quickly, allowing the oxygen to escape into the air, cleansing the CMS for the next cycle. The Sieve bed is then re-flooded with pressurized air and the cycle begins again.


To gather oxygen, the Zeolite has larger porous surfaces, which attract the nitrogen molecules. As both oxygen and nitrogen flow through the Zeolite, the oxygen moves freely past, while the nitrogen is captured. This is because the Zeolite has an affinity for the nitrogen. The same process then takes place, the oxygen molecules are free floating and are drawn off into a storage tank. When these have been drawn off, the tanks are then purged ready for the next cycle.

Our PSA generators come as standard with an inbuilt oxygen analyzer so your purity is measured and displayed on the touch panel in real time. For our nitrogen systems, we have a patented Purity Exchange Valve which lets you choose three different purities with the one system – all controlled via the touch screen control panel.


95%, 97%, 98%, 99%, 99.5%, 99.9%, 99.95%, 99.99%, 99.995%, 99.999%, 99.9995%


90%, 93% USP grade (+/- 3%), 93%, 95%, FDA cleared medical oxygen, TGA approved medical oxygen (for military POGS)

We expect about 20-25 years life from a PSA Nitrogen system and we know we get 15–18 years in a PSA Oxygen system. Membranes are a different story. Since the membranes start degrading immediately and level off after one year, a unit will over-perform at first, however, if you are putting high-pressure air through the membrane and/or pushing high volumes of air through the unit to increase flow, the unit will need replacement in about 5 – 7 years.

Our technology is designed around using the simplest and most direct path to achieve the goal. We seek reliability through simplicity. We use all off-the-shelf parts so that our systems can be serviced by any mechanically inclined person, anywhere in the world. We have worked with and tested all technologies involving PSA gas production and continue to find that our time-proven basic technology, constantly tweaked and upgraded with innovation, makes the most reliable system in the world. The true genius is to make a complex process simple and understandable; then keep it that way.
However, saying that, just ask us and we will be glad to put you in touch with any of our long standing customers. Most of the time the answer you will hear is that they forget the system is even there. Don’t just believe what we say, talk to people who use the system and let them tell you the real story.

PSA technology relies on the principle of adsorption rather than chemical reactions. Compressed air is used to pressurise a vessel containing carbon or zeolite, which selectively traps either nitrogen (N2) or oxygen (O2) molecules while allowing the other gas to escape freely. By cyclically pressurising and releasing the vessel, a consistent flow of the desired gas is achieved. PSA systems can deliver high-purity gases, up to 99.999%, making them suitable for critical applications.

PSA technology operates based on the principle of adsorption. It utilises a bed of adsorbent material, typically carbon molecular sieve or zeolite, to selectively adsorb certain gas molecules while allowing others to pass through. The process involves cyclic pressure changes to separate the desired gas from the feed gas mixture. PSA systems are known for their reliability, versatility, and ability to produce gases with high purity levels, often up to 99.999%.ordion Content

Membrane technology relies on semi-permeable membranes that selectively allow certain gas molecules to pass through while restricting others based on their size and permeability. By utilising this separation mechanism, membrane systems can effectively generate nitrogen or oxygen with moderate purity levels, typically up to 99.5%. Membrane systems are usually compact, require less maintenance, and have lower capital costs compared to PSA systems.

The main difference between PSA and membrane technology lies in their respective capabilities and cost-effectiveness. PSA technology offers higher purity levels and greater flexibility in gas production, making it the preferred choice in applications that demand ultra-high purity gases, such as electronics manufacturing, pharmaceuticals, and food packaging. Additionally, PSA systems can handle varying feed gas compositions and flow rates more efficiently than membrane systems.

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