How does an Oxygen Concentrator Work?

by Justin LaClair January 14, 2019 6 min read

How does an Oxygen Concentrator Work?

An Oxygen Concentrator is a machine that draws in ambient air from the room around it, removes most of the Nitrogen, and passes the pure Oxygen to the patient.

There are some main components that make up an Oxygen Concentrator:

  • Air Filters
  • An Air Compressor
  • 4 way switching valves
  • Sieve Beds
  • Circuit Board
  • Product Tank

Air Filters:

Every Oxygen Concentrator has a series of filters used. The job of these filters is twofold. Some of the filters work to clean the air before it goes through the Compressor, and some of the filters clean the air before it leaves the machine and is provided to the patient.

The cabinet filter is typically a piece of foam that sits in the exterior cabinet of the Oxygen Concentrator. It is used to stop large items like lint or pet hair from getting inside of the Oxygen Concentrator. These filters are recommended that you rinse them off in your sink every week or two, and let them dry before placing them back in the machine.

The HEPA filter is generally a pleated paper material encased in a plastic housing. These filters are not serviceable. Do not attempt to clean them. Simply throw them away and replace them once a year. The purpose of this filter is to clean the air before it goes directly into the compressor. As the filter gets dirty, you may observe the white paper is turning black where the air enters the filter. This is normal, and proof that the filter is doing its job! As the machine is used more and more, you will see that the paper filter inside will turn all black. Again, this is normal, and shows how well the filter is working. The more dirt the filter keeps out of your compressor, the longer the compressor will last!


The compressor inside of an Oxygen Concentrator is typically a "Double Wobble" style motor. This means that it has two pistons inside of it that spin extremely fast, to pull in ambient air from the room around the Oxygen Concentrator, compress the air, and push it through the rest of the Oxygen Concentrator. Outlet pressure from the compressor is normally around 15PSI. The compressors can last anywhere between 8,000 and 15,000 hours (depending on the type of compressor). After this life cycle, the compressor typically will need some maintenance. Think of it like an oil change for your car. It is cheap maintenance to keep your entire Oxygen Concentrator running for many years.

Four Way Valves:

The Four Way Valves are a very simple item, but are just as crucial to the proper operation of the Oxygen Concentrator as any other piece. The valves are used to direct air from the Compressor to the pair of Sieve Beds, and also directs the Nitrogen waste gas back into the room atmosphere. Depending on the Oxygen Concentrator you have, the valves can be operated by a timer on the circuit board, or could be operated based on the operating pressures of the rest of the machine. The latter gives the machine the ability to adapt itself to run efficiently as the machine ages and it may take a longer time to achieve optimal running pressures. If your valves malfunction, it will cause low output Oxygen purity, or can also cause high or low internal operating pressures which will typically make your Oxygen Concentrator alarm and not function properly. Some valves in older machines like an Airsep Elite are powered by electronic coils that move large metal plungers when the coils are energized. They emit a mechanical clunk every 10-12 seconds, and typically never have any issues while operating. Most other valves like you may find in the very popular Respironics EverFlo are also powered by electronic coils, but they are very small and quiet, but may be more susceptible to failing.

Sieve Beds:

Sieve Beds are definitely a crucial part of the Oxygen Concentrator, but again, every component we discuss is just as important as the next! Sieve beds are pretty "simple". Typically found in pairs, they are full of a material called Zeolite. As defined by Wikipedia; "Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts." Zeolite found in an Oxygen Concentrator looks similar to sand. If put under a microscope, each grain will have a very porous appearance. This provides more surface area to make Oxygen. As the ambient air makes its way through the previously discussed components, it will be directed into a Sieve Bed. As the air is forced into one Sieve Bed, it becomes highly pressurized inside. When Zeolite is pressurized like this, its properties change, and it becomes a Nitrogen Magnet, but allows the Oxygen to pass through! Once the Sieve Bed is fully pressurized, the Four Way Valves will switch the air to fill the second Sieve Bed. This abrupt switching from One Sieve Bed to the next allows the first Sieve Bed to rapidly depressurize. This leads to the "whoosh" or "breathing" sound your Oxygen Concentrator makes. This is a totally normal sound, and is vital to the Oxygen Concentrators proper operation. Once the second Sieve Bed pressurizes, the process restarts all over again. Every 10-12 seconds, you will generally hear this rhythmic breathing sound. Sieve Beds found in newer Oxygen Concentrators like the Devilbiss 525DS, Respironics Everflo, or Invacare PerfectoV all contain a highly efficient Zeolite material that used to be exclusive to the much larger 10LPM stationary Oxygen Concentrators. Using this very efficient material for a 5LPM Oxygen Concentrator gives the ability to manufacture a much smaller Oxygen Concentrator, since much less Zeolite is needed to provide the 5LPM of Oxygen to the Patient.

Circuit Boards:

The circuit boards inside of an Oxygen Concentrator are like the brains of the operation. They can control everything from the compressor, to the four-way valves, and sometimes even the cooling fan operation. As previously mentioned, depending on the machine you have, the circuit board can control your machine based off of set timing, or could run off of the operating pressures of the machine. Either style is very reliable. Circuit boards generally need no maintenance. Depending on your machine, it may also have a built in Low Purity Sensor. This sensor is generally installed into the main circuit board and will need at least one Oxygen tube run from the Sieve beds to the circuit board so it can continually monitor the purity of the Oxygen that the Oxygen Concentrator is making. While rare, some Oxygen Concentrators like the Respironics Millennium can have a second, separate circuit board that is used specifically for the Low Purity Sensor.

Product Tank:

One of the last "large" components inside of an Oxygen Concentrator is going to be the Product Tank. The Product Tank is an intermediate tank. Each Sieve Bed sends its Oxygen into the Product Tank. Each Sieve Bed may produce different Oxygen purity. The Product Tank allows the Oxygen from both Sieve Beds to mix inside of it, which will provide a nice steady Oxygen Purity to the patient. It also acts as a buffer to stabilize any differences in pressure between the Sieve Beds. While rare, some machines like the Airsep Elite have a Product Tank that is full of Zeolite, and acts as a "Mini Sieve Bed" to help increase Oxygen Purity just a little before it is sent to the patient! Product Tanks in this particular machine will need to be replaced as needed, due to the Zeolite inside wearing out.

But Wait, There's More!!

After the Oxygen leaves the Product Tank, it exits the Oxygen Concentrator and is delivered to the Patient! But, not before passing through one last filter! The Bacteria Filter is an in-line filter that is placed before the Oxygen Outlet inside of the Oxygen Concentrator. It sometimes looks like a top. The job of this filter is to stop any very fine particulates from exiting the machine. On most newer machines, this filter has very recently been reclassified as a "lifetime filter" and never needs to be changed. We still recommend changing it at least every 2 years, or every time the machine is to be placed on a new Patient.

That is the basic operation of how an Oxygen Concentrator works! Keep in mind, annual filter changes are a great idea! The cleaner the air that goes through your Oxygen Concentrator, the longer all the components we just discussed should last!

As always, feel free to contact us via email at or by phone at 1-540-297-3257 if you have any extra questions or concerns!


Justin LaClair
Justin LaClair

Justin has been working with OxygenPlus since their storefront start in 1993. In 2002 he earned the title of CEO and has been operating OxygenPlus ever since. Most of the time if you call, Justin will answer the phone. He tries to be extremely hands on with most every transaction that takes place. Raised with a very high quality standard, any work must meet his satisfaction before it is approved. He is a classic car enthusiast, loves traveling either for work or pleasure, and is a renewable energy advocate. As of 2015, he saw to it that his personal home, and OxygenPlus Medical run 100% off of solar power.

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