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How Does an Oxygen Sensor Work?

An oxygen (O2) sensor senses the percentage of oxygen in the air being delivered to an oxygen therapy patient. Oxygen sensors are placed in in oxygen concentrators to ensure proper creation and delivery of oxygen. The Inogen One G4 is equipped with an internal oxygen sensor that will alarm should the O2 concentration go below a therapeutic range.[1] Why should the O2 concentration delivered to the patient be kept at a therapeutic range? Let’s have a look and see!

The Importance of Oxygen Purity

oxygen sensor, how does an oxygen sensor work, Inogen One G4One of the most important characteristics of an oxygen concentrator is the purity of oxygen it’s able to deliver to a patient. After all, when purchasing an oxygen concentrator, you trust it will be able to maintain a specific level of oxygen purity, at a certain setting, to deliver the precise amount of oxygen you need to preserve your health. Of course, the exact amount of oxygen you need is determined by your doctor or lung specialist, who prescribed it to you, to compensate for the amount of oxygen your lungs aren’t able to take in.[2]

It’s fairly easy to check the purity of your oxygen concentrator to ensure you’re receiving the proper amount of oxygen. In addition, maintaining and caring for your oxygen concentrator on a regular basis will ensure that your concentrator will continue to deliver oxygen at the highest purity level possible.2

Please note: if you ever start to feel bad and you know you’re not having an exacerbation (flare-up) of your medical condition, it could mean that the purity of the oxygen in your concentrator has declined which is when you’d want to put it to the test. Find out how to do that in the following section. 2

Testing the Oxygen Purity of your Inogen One G4

If you’re ready to test the oxygen purity of your Inogen One G4, take the following steps:[3]

  1. Start by turning your Inogen One G4 off. Once your unit is in the “Off” Mode, attach the AC power supply and nasal cannula.
  2. Press and hold both the “Plus” button and the “Bell” button at the same time until the screen displays “Mode Select: Normal”.
  3. Press the “Plus” button one time; the screen will display “Mode Select: Autopulse”.
  4. Press the “Bell” button once to activate the sub-menu; the screen should display “Autopulse: 17 BPM”.
  5. Press the “Bell” button once and the Inogen One G4 will start up in “Autopulse Mode”.
  6. Allow your unit to run in “Autopulse Mode for 45 minutes to enable it to complete a thorough diagnostic test. If a problem occurs, you will see an error message on the screen.

O2 Purity Screen

  1. Once the unit has run for 45 minutes, you may read the purity level.
  2. Press and hold the “Bell” button.
  3. After 5 seconds, the screen will display the life clock, software version and serial number along with some blank dashes. You should now release the “Bell” button and press and hold the “Plus” Button until a light blue screen appears with the words “Pulse Testing”
  4. Wait 10 minute and the dashes will be replaced with the oxygen purity percentage of your unit.
  5. Press the “Plus” Button once and the O2 purity screen will disappear.3

Why Is My Unit Registering a Low Purity Level?

There are several reasons why an oxygen sensor would alarm causing an oxygen concentrator to register a low purity level:3

  1. It’s an older model that hasn’t been refurbished properly.
  2. There is a malfunction in the unit itself.
  3. One of the filters hasn’t been cleaned when it was supposed to be cleaned.

Particle Filters

The Inogen One G4 comes equipped with a particle filter that needs to be cleaned weekly to ensure maximum ease of airflow. The particle filter should be washed in warm water with a mild dishwashing detergent such as Dawn. You should then rinse it in warm water and allow it to air dry before using it again. You can purchase additional Inogen One G4 particle filters through the Inogen website, here.3

Remember: if your oxygen sensor keeps alarming, it means the oxygen concentration in your unit has fallen below a therapeutic level. This could lead to low oxygen levels in the blood and other serious health problems. Make sure your oxygen concentrator is well-maintained so problems like this don’t arise unexpectedly.

[1] ServoFlo. Pressure and Oxygen Sensors in Oxygen Concentrators. Accessed February 28, 2018.

[2] Oxygen Concentrator Store. How to Check the Purity of Your Oxygen Concentrator.  Accessed February 28, 2018.

[3] Inogen One. Testing O2 Purity. Accessed February 28, 2018.


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