Best Oxygen Nitrox Analyzer for Scuba Diving (Pro Guide)

Nitrox Analyzer, Oxygen Analyzer, Oxygen Detector -

Best Oxygen Nitrox Analyzer for Scuba Diving (Pro Guide)

An Oxygen Nitrox Analyzer is a critical tool used by divers to check and confirm the oxygen levels within their gas cylinders. It is paramount the oxygen analyzer is consistent and reliable in checking the oxygen levels in your cylinder as gas safety and air inhalation during diving is of the upmost safety concern. Oxygen nitrox analyzers used for scuba are sometimes referred to as a Scuba Analyzer, Nitrox Analyzer, or simply as an Oxygen Analyzer. They are easy to use and present the user with a digital oxygen concentration in %vol of the tested gas from the gas cylinder.



  • Allows divers to verify their oxygen levels before a dive.
  • Provides divers with a verification mechanism when purchasing enriched oxygen cylinders.
  • Oxygen nitrox analyzers now less than $200.
  • Oxygen Nitrox Analyzers are not cheap.
  • Oxygen nitrox analyzers may require calibration before use.
  • Oxygen nitrox analyzers use electrochemical cells, which reduce in voltage output over time and require to be replaced every 2-3 years.

What is a Oxygen Nitrox Analyzer?

A Nitrox analyzer, or an Oxygen nitrox analyzer, is a device commonly used in the scuba diving community to test and verify oxygen levels within a tank.

When Should I use an Oxygen Nitrox Analyzer?

It is good practice to check each tank before diving as a safety measure. A Nitrox analyzer ensures that the oxygen and nitrogen blend is as ordered or as expected. Most dive shops require the diver to analyze the cylinder contents before signing off and taking ownership of the tank.

If you are diving in a group, ensure an oxygen nitrox analyzer is present on the boat or check your cylinders before leaving home or the fill station.

Who needs an oxygen nitrox analyzer for scuba?

  • Divers: Oxygen nitrox analyzers are used by divers and equipment technicians to verify oxygen concentrations within the tank.
  • Dive Shops: These are used in dive shops for verification purposes at dive fill stations.

What is Enriched Air Nitrox?

Diving is mainly undertaken using compressed air. That is, normal fresh air with nominal oxygen concentration of 20.9%.

However, there is an alternative, and that is Enriched Air Nitrox, sometimes abbreviated as EAN or Nitrox for short. Nitrox is a gas mixture with increased oxygen beyond 20.9% (normal air). 

Most if not all World Recreational Scuba Training Council (WRSTC) training agencies recognize Enriched Air as any oxygen and nitrogen gas mixture with a partial pressure of oxygen above 20.9%.

Recreational mixes range between 21%-40%, with the most common mixes being 32% and 36%.

Typically, Nitrox cylinders are marked green with a yellow diagonal thick line or simply with a green and yellow sticker with the words NITROX or ENRICHED AIR.

Special training and certification is required for the safe handling and use of Nitrox mixes (either for Recreational diving or Technical diving).  Dive Shops require a valid Nitrox or Advanced Nitrox certification before filling a diver’s tanks.

How does an Oxygen Nitrox Analyzer Work?

An oxygen nitrox analyzer is made up of two main components.

  • The electronics that has a on-board digital processor along with an analog to digital converter. 
  • The electrochemical oxygen sensor is actually a galvanic cell that outputs electrical energy from the electron transfer in a redox reaction modulated by the oxygen being detected. The oxygen sensor is a partial pressure sensor that outputs a voltage proportional to the oxygen concentration. The most in-depth article on oxygen sensors is by Mr. Paul Raymeakers.

When the unit is "calibrated", it undertakes a linear extrapolation from zero to 20.9% (or a different span calibration value), and based on this two-point linear regression, the digital processor translates that output voltage from the sensor to an oxygen concentration which is then displayed to the user.

Most often, oxygen nitorox analyzers are calibrated in the air to 20.9%. However, to improve accuracy, calibrating at a higher oxygen concentration (i.e., 35%) will increase accuracy when detecting oxygen in Nitrox filled cylinders.

The closer you calibrate your oxygen nitrox analyzer to the expected tank oxygen concentration the higher the accuracy of your measurement. The problem, however, is that a separate certified gas calibration bottle is required.

    Does an Oxygen Nitrox Analyzer require special training?

    No, it doesn’t. Most of them are very simple to use. Each oxygen nitrox analyzer has it quirks. However in general, turn ON, ensure 20.9% in the fresh air, then test. Be smart and read the user manual to familiarize yourself with your oxygen analyzer model. 

    How is an Oxygen Nitrox Analyzer used?

    In general, it goes something like this:

    • First, ensure the unit is calibrated to display 20.9% when in the fresh air.
    • Place the dome fitting or similar fitting directly onto the cylinder valve.
    • Carefully turn ON the valve for about 10 seconds.
    • The oxygen level will increase.
    • Take the maximum oxygen reading. If it is still increasing, continue to test beyond 10 seconds. Once the oxygen digits and level have tapered off, turn the gas off and note the O2 reading.
    • Make sure the oxygen concentration matches what you purchased or what you expect.
    • Store your oxygen nitrox analyzer properly.

      Tips when Selecting an Oxygen Nitrox Analyzer?

      Make sure the analyzer has the following:

      • Accessories: Ensure the analyzer comes with the necessary accessories to undertake a direct to valve test. Typically this is a dome attachment piece. A dome is very important to control the amount of "blast" air that the sensor "feels". Make sure there is some limiting dome accessory. This is important since just blasting air onto the sensor will give very inaccurate oxygen readings as this changes the atmospheric pressure the sensor experiences.
      • Oxygen Sensor: What type of sensor and which brand sensor is included within the analyzer? It is important to ensure the sensor comes from a reputable brand with a proven track record, such as Honeywell, Teledyne, etc... Take note of the lifespan, usually, sensors have a lifespan of 24 to 36 months.
      • Detection Range: Make sure the analyzer can detect up to 100% oxygen. Common Recreational diving Nitrox mixes can range anywhere from 22%-40%.  Technical diving enriched oxygen mixes are typically 50%, 80%, or even 100%. Some oxygen nitrox analyzers only detect oxygen levels from 0-30% and obviously will not suffice for diving. Ensure your oxygen analyzer detects from 0 to 100% with 0.1% resolution.

      What are the best Oxygen Nitrox Analyzers for Scuba?

      There are several oxygen nitrox analyzers that compete for your business. The most popular include:

      Which is our top Nitrox Analyzer pick?

      We are fans of the new kid on the block, the Forensics Detectors Oxygen Analyzer for Scuba. It was launched in 2020 and one of the newest oxygen nitrox analyzers on the market.

      • It is a basic unit but comes with a Honeywell medical-grade oxygen sensor that lasts up to 36 months.
      • The package comes with a waterproof case, accessories for direct-to-tank testing or in-line testing.  
      • The unit has one-button quick fresh air calibration and takes 3 x AAA batteries.

      You will never find this unit priced over $199. We are happy and proud we have broken the $200 price point for such a product that has traditionally been well over $200 and often retails in the $300s.

      What do customers think?

      Reviewed in the United States on August 6, 2020

      I wasn't sure about this unit because there were no reviews. After testing three separate nitrox scuba tanks in both 32 and 36 percent gases, I trust this oxygen analyzer to test my scuba gases in the future. 

      What about Carbon Monoxide Analyzers for Scuba?

      Carbon monoxide analyzers are different than oxygen nitrox analyzers. They detect trace amounts of carbon monoxide that may have unintentionally entered the supply of your gas mix. Typically this may happen when exhaust gas from the compressor used to fill the tank cylinder enters the air stream.

      What about Helium Analyzers for scuba?

      Helium Analyzers are used with trimix gas. Trimix is a gas mixture of air, helium, and oxygen. A helium analyzer is used by technical divers to confirm, and verify their trimix gas cylinders.

      Final Words

      • Make sure to never purchase an oxygen nitrox analyzer used as the actual age of the device is unknown.
      • Make sure to take note when you purchased the oxygen nitrox analyzer and track its age to ensure you do not exceed the specific lifespan of the sensor.
      • Make sure that you always calibrate before measurement. To enhance accuracy, technical fill stations often use dry gas for calibration.
      • Ensure replacement sensors are available and can be easily replaced.
      • Store your analyzer at a nominal room temperature. Refrain from storing the analyzer in high humidity or low dry humidity. Keep it somewhere in the middle of the RH% range.

      About The Author

      Dr. Koz is the President of FORENSICS DETECTORS, where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters, and gas analyzers. He has been designing, building, manufacturing and testing toxic gas detection systems for over 20 years.

      gas detector expert

      Every day is a blessing for Dr. Koz. He loves to help customers solve their unique problems. Dr. Koz also loves spending time with his wife and his three children going to the beach, grilling burgers, and having a cold beer. 

      Read more about Forensics Detectors here.

      Phone: +1 424-341-3886


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