Best Oxygen Nitrox Analyzer (for Scuba Diving)

An oxygen nitrox analyzer is a critical tool used by divers to confirm the oxygen levels within their gas cylinders. It is essential that the oxygen analyzer is reliable as air inhalation during diving is the biggest safety concern. Oxygen nitrox analyzers used for diving are also referred to as a scuba analyzers, nitrox analyzers, or simply as oxygen analyzers. They are easy to use and display the oxygen concentration in %vol of the gas cylinder.

Pros	Cons
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.	While oxygen nitrox analyzers can be puchased for less than $200, they are still not cheap. Oxygen nitrox analyzers may require calibration before use. Oxygen nitrox analyzers use electrochemical cells, which lessen in voltage output over time and must be replaced every 2-3 years.

What Is an Oxygen Nitrox Analyzer?

A nitrox analyzer, or an oxygen nitrox analyzer, is a device commonly used in the scuba diving community to test levels within an oxygen 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 mixture is as expected. Most dive shops require the user to analyze the cylinder gas contents before signing off and taking ownership of the tank.

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

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 performed using compressed air. This is fresh air with a nominal oxygen concentration of 20.9%.

However, enriched air nitrox (EAN), or Nitrox for short, is a common alternative. Nitrox is a gas mixture with increased oxygen beyond 20.9%. 

World Recreational Scuba Training Council (WRSTC) training agencies recognize enriched air as any oxygen and nitrogen gas mixture with an oxygen partial pressure above 20.9%.

Recreational mixes range from 21% to 40%, with the most common proportions ranging between 32% and 36%.

Typically, nitrox cylinders are marked green with a thick, yellow 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 in both recreational and 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 consist of an on-board digital processor along with an analog to digital converter. 
• The electrochemical oxygen sensor, a galvanic cell that outputs electrical energy. This signal comes from the electron transfer in a redox reaction modulated by the detected oxygen. The partial pressure sensor outputs a voltage proportional to the oxygen concentration. The most in-depth article about oxygen sensors is by Mr. Paul Raymeakers.

When the unit is "calibrated," it creates a linear extrapolation from 0% to 20.9% (or a different calibration value). Based on this two-point linear regression, the digital processor translates the voltage from the sensor to an oxygen concentration, which is then displayed to the user.

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

Calibrating your oxygen nitrox analyzer more closely to the expected tank concentration will result in more accurate measurements. This requires a certified gas calibration bottle.

Does an Oxygen Nitrox Analyzer Require Special Training?

No, it doesn’t. Most analyzers are very simple to use, although each has it quirks. In general, turn the device ON, ensure that it measures 20.9% in fresh air, and then test. Be smart and read the user manual to familiarize yourself with your specific model. 

How Is an Oxygen Nitrox Analyzer Used?

In general, operation of an oxygen nitrox analyzer follows these steps:

• First, ensure the unit is calibrated to display 20.9% when in fresh air.
• Place the dome fitting directly onto the cylinder valve.
• Carefully turn ON the valve for about 10 seconds.
• Allow the oxygen level to increase.
• Take the maximum oxygen reading. If it is still increasing, continue to test beyond 10 seconds. Once the oxygen level has leveled out, turn the gas off and note the O2 reading.
• Make sure the oxygen concentration matches the noted concentration on the cylinder.
• 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 perform a direct to valve test. This is typically a limiting dome attachment piece. A dome is necessary to control the amount of "blast" air that the sensor "feels." Blasting air directly onto the sensor will give inaccurate readings due to changes in atmospheric pressure.
• Oxygen Sensor: What type of sensor and which brand 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, sensors typically have a lifespan of 24 to 36 months.

• Detection Range: Make sure the analyzer can detect from 0% to 100% oxygen, with 0.1% resolution. Common recreational diving nitrox mixes can range anywhere from 21% to 40%. Technical diving enriched oxygen mixes are typically 50%, 80%, or even 100%. Some oxygen nitrox analyzers only detect oxygen levels from 0 to 30% and will not suffice for diving. 

What Are the Best Oxygen Nitrox Analyzers for Scuba?

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

• Analox Oxygen Analyzer 02EII Pro for Scuba Divers
• Analytical Palm 02 Analyzer
• Oxygen Analyzer O2BOX for Scuba by Forensics Detectors
• Maxtec New Oxygen Analyzer for Nitrox Scuba Diving
• Nuvair O2 Quickstick Oxygen Analyzer

Which Is Our Top Nitrox Analyzer Pick?

We are fans of the new kid on the block, the Forensics Detectors Oxygen Analyzer for Scuba. Launched in 2020, it is one of the newest oxygen nitrox analyzers on the market.

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

You will never find this unit priced over $199. We are proud to have broken the $200 price point for a product that traditionally costs well over $200, even into 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. This may happen when exhaust gas enters the air stream from the compressor used to fill the tank cylinder.

To detect carbon monoxide gas, once requires a very sensitive CO meter. Forensics Detectors has developed a very low CO meter that detects down to 0.1ppm of CO gas. This perfect to detect low amounts of carbon monoxide that may have been unintentionally compressed in your gas cylinder.

What About Helium Analyzers for Scuba?

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

Final Words

• Make sure to never purchase a used oxygen nitrox analyzer, as the actual age of the device is unknown.
• Make sure to note when you purchased the oxygen nitrox analyzer and track its age to ensure you do not exceed the 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 installed.
• Store your analyzer at a nominal room temperature. Refrain from storing the analyzer in high or low 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. 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. Email:  drkoz@forensicsdetectors.com Phone: +1 424-341-3886