Best Oxygen Detector (O2 Purity and Depletion)

Oxygen (O2) detectors are one of the most essential gas analyzers due to the necessity of oxygen for human life. These important safety devices alarm when oxygen levels drop significantly to help avoid occupational dangers. An oxygen detector is a handheld unit that instantaneously detects the O2 levels and displays it on the digital screen. In recent years, the price of oxygen detectors has dropped and can be purchased for less than $200.

Why Is Oxygen (O2) Gas So Important?

Oxygen helps sustain the majority of life on Earth. Without oxygen, our planet would be lifeless because humans and animals need it to survive. When O2 levels decrease, oxygen deficiency can occur at a dangerous rate and lead to asphyxiation. An oxygen detector is important to alert humans of decreasing O2 levels.

O2 is the chemical formula for oxygen. 20.9% of the air around us is made up of oxygen. Detecting oxygen levels is very important in our everyday lives. Some examples include:

• Detecting oxygen in manufacturing processes. Being aware of both enriched and depleted oxygen levels is necessary.
• Detecting oxygen in life support systems such as those used in spacecrafts, aircrafts, submarines, and vet hospitals. 
• Detecting oxygen in gas bottles used in scuba diving.
• Detecting oxygen to help support human and animal health.
• Detecting oxygen to confirm that little or no oxygen exists, including welding, modified atmosphere packaging, or nitrogen flush purging processes.
• Detecting oxygen in welding torches

What Does an Oxygen Detector Do?

Oxygen detectors measure the amount of oxygen in the air as a %. An oxygen detector is a handheld unit with alarms that alert users of dangerous levels.

Oxygen detectors are also called oxygen meters, oxygen monitors, or oxygen analyzers. They all refer to an oxygen measuring instrument that can measure the O2 concentration in %vol or parts per million (ppm), alarming when these levels fall outside of the preset range.

How Does an Oxygen Detector Work?

An oxygen detector works by using an electronic sensor to detect O2 concentrations. The most common sensor used for oxygen detectors is an  electrochemical sensor cell.

An oxygen detector is made up of two main parts:

• The electronics consisting of microprocessors with analog to digital converters. 
• The electrochemical oxygen sensor. This galvanic cell outputs electrical energy from the electron transfer in a redox reaction modulated by the oxygen being detected. The partial pressure sensor outputs a voltage proportional to the oxygen concentration. 

When the oxygen detector is "calibrated," it is able to detect oxygen from 0 to 30% (as an example). A linear extrapolation take place from the from zero point calibration (usually pure nitrogen) to 20.9% (air oxygen concentration). 

How Does an Oxygen Sensor Work?

The most common electrochemical oxygen sensor is the Alpha Sensor (see below). Its profile, dimensions, and working principle is similar to many other electrochemical sensor cells.

When oxygen gas molecules permeate into the sensor, they react with a working electrode and trigger an electrochemical redox reaction. A current is generated proportional to the oxygen level detected.

What Are the Different Types of Oxygen Detectors?

Type	Description
Oxygen Detector for Personal Protection	The majority of oxygen detectors are portable and can be clipped to your person. These are small, battery-powered units with an oxygen sensor that enable continuous personal protection.
Oxygen Detector with Pump for Point Sampling	This is an oxygen detector with a built-in or external pump. When these devices have a built in pump, they are also called oxygen analyzers. A probe is used to enable point sampling. These analyzers are used to detect oxygen content for food packaging, welding, and nitrogen purging applications in industry.
Oxygen Detector for Stationary Fixed Wall	Wall-mounted units provide continuous protection. These units are more expensive and offer protection in an industrial facility or other confined spaces.

What Is the Difference Between Different Oxygen sensors?

What Is Oxygen Deficiency?

Oxygen deficiency is life-threatening and cannot be detected by our sense of smell. In general, oxygen deficiency is caused by the release of inert gases, which then in turn displace oxygen.

Because roughly one-fifth of the atmosphere is oxygen, the O2 concentration is only reduced by one-fifth of the concentration of inert gas. For example, if 10% of helium is released into the atmosphere, the oxygen concentration decreases by 2% and the nitrogen concentration is reduced by 8%. Because liquid nitrogen (-196 °C) is often used in industrial areas, dangerous levels of oxygen deficiency can occur due to the evaporation of this liquid nitrogen.

What Are Safe Oxygen Levels?

When oxygen levels decrease, it becomes dangerous to humans and animals (typically less than 19.5%). Oxygen deficiency causes humans to basically suffocate, also known as asphyxiation. This can be a big problem in occupational environment such as confined silos, tanks, manholes, tunnels, and chambers.

When humans breath low oxygen, healthline.com describes the following possible symptoms of hypoxia:

• Shortness of breath while resting
• Severe shortness of breath after physical activity
• Decreased tolerance to physical activity
• Waking up out of breath
• Feelings of choking
• Wheezing
• Frequent cough

Various government agencies have recommended oxygen gas limits. Some examples are shown in the table below.

Are High Levels of Oxygen Dangerous?

High levels of oxygen, also known as hyperoxia, causes oxygen toxicity. This oxygen poisoning may damage the lungs or cell tissue, cause trouble breathing, and induce coughing.

An oxygen detector typically has two alarms. The first is a low alarm that triggers when oxygen levels decrease past a set-point. The second is a high alarm that goes off when enhanced oxygen levels occur.

What Is an Oxygen Detector Used For?

There is a plethora of applications that call for the use of an oxygen detector. Some of these uses are highlighted below.

• Veterinary: Oxygen therapy is administered to animals under various situations. An oxygen analyzer is necessary to ensure the correct amount of O2 is being provided to the animal.
• Food Packaging Analysis: Used in many food industries as a quality control check to ensure modified atmosphere packaging equipment is operating correctly. Typical requirements include an O2 measurement range from 0 to 100%, with 0.01% resolution and built-in pump. 
• Nitrogen Flush and Leakage Testing: Many industrial systems and equipment incorporate nitrogen gas supply, where monitoring of leaks is essential. This is done by detecting residual oxygen. Typical requirements include an O2 measurement range from 0 to 100%, with 0.01% resolution and built-in pump.
• Scuba Tank Oxygen Supply: Scuba divers use air cylinders and enhanced oxygen air supply when diving. Before using the cylinders, they often use oxygen analyzers to validate the oxygen concentration. Typically requires O2 analyzers to detect enhanced oxygen levels ranging from 21 - 100%.
• Flue and Exhaust Gas: Combustion processes are fueled by oxygen. In most cases, oxygen is measured to help optimize the air-to-fuel ratio. This occurs in automobiles, gas powered appliances, and more sophisticated combustion processes such as power generation. Typical requirements include an O2 measurement range from 0 - 20.9% with 0.1% resolution. 

How Can I Test My Oxygen Analyzer?

The best way to test your oxygen detector is to expose it to nitrogen. Since air is made up of 20.9% oxygen, bump testing it to pure nitrogen and perturbing the amount of O2 is a valid check. If your analyzer has alarms, it is important to verify that they are operational. Spray the gas onto the sensor to confirm sensor and LED and buzzer alarm operation. 

Will My Oxygen Detector Alarm If I Breathe on It?

If you breath onto your oxygen detector, the detected O2 levels will quickly decrease as exhaled breath has depleted oxygen levels of approximately 17%. The below video analyzes oxygen exhalation.

What Is the Best Oxygen Analyzer Brand?

There are many oxygen analyzers on the market. The reputable brands used to detect elevated oxygen levels from O2 sources and concentrators include the following:

• Forensics Detectors Oxygen Detector
• RKI Oxygen Detectors
• Analox Oxygen Detectors
• Analytical Industries Oxygen Analyzer
• Oxygen Analyzer by Forensics Detectors
• Maxtec New Oxygen Analyzer
• MSA Oxygen Gas Detectors
• Honeywell Oxygen Gas Detectors
• Draeger Oxygen Detectors
• Teledyne Oxygen Detectors

How Do I Select an Oxygen Detector?

To select the best oxygen detector that serves your purpose, follow this guide. In order to narrow down your selection, first answer these questions:

• What oxygen detection range do I need?
• What resolution do I need?
• How often will I use it?
• What is my budget and operating cost budget?
• Does my application require any special product requirements? Do I need a pump, accreditations, or a waterproof device?
• Do I need advanced functions such as battery operation? Detection of flow or pressure?
• Do I need a stationary fixed wall unit?

Based on these answers, you can quickly narrow down a product for your purpose. You may need to compromise on certain features to adjust for your budget.

What Are Specialized Oxygen Detectors?

Some applications have unique requirements when it comes to oxygen detection. Each situation calls for special oxygen detector function specifications, measurements, and attributes. Examples include the following:

• Oxygen Detection for Scuba Gas Bottles
• Oxygen Detection for Oxygen Concentrators
• Oxygen Detection for Food Headspace Analysis
• Oxygen Detection for Breath Analysis
• Oxygen Detection for Welding Applications
• Oxygen Detection for Flue Gas (residential)
• Oxygen Detection in Workplaces

How Long Do Oxygen Detectors Last For?

An oxygen detector that employs electrochemical sensors will last between 24 to 36 months. 

Can an Oxygen Gas Detector Measure Dissolved Oxygen?

No, it cannot. To measure dissolved oxygen (DO), a specific O2 meter for water must be purchased. An oxygen gas detector only measures oxygen content in air. A detector with different technology is required to measure oxygen in water, more commonly referred to as dissolved oxygen.

Is It Better to Detect Oxygen or Carbon Dioxide for Indoor Air Quality?

It is better to measure carbon dioxide. A CO2 monitor will detect carbon dioxide levels with 1 ppm resolution. A oxygen detector will measure, at best, 0.1% resolution (which is 1000 ppm). In other words, CO2 detection will allow for higher sensitivity and measurement fidelity. With similar detector qualities (including price), the better option is to measure CO2 for basic home indoor air quality.

However, if you're in a "confined space," then using an oxygen detector is recommended. 

Is It Worth Replacing My Oxygen Sensor in My Oxygen Detector?

Some manufacturers offer replacement oxygen sensors, while others do not. Gas sensor replacement is a very lucrative business model. The cost effectiveness strongly depends on the price of a new unit. 

In most instances, the cost of replacing a sensor outweighs the cost of purchasing a new gas detector unit. Consider the cost analysis below of these two scenarios.

** Scenario A: Purchasing a New Oxygen Detector

Model FD-90A-O2. Portable oxygen detector. Retail Price: $145

** Scenario B: Cost of an Oxygen Sensor Replacement

New O2 Sensor = $95

Engineer time to replace = 15 min @ $100/hr = $25

Calibration to NIST traceable gas = 15 min @ $100/hr = $25

Administration overhead = 10 min @ $60/hr = $10

Total = $155

Analysis = $145 (new detector) versus $155 (replacement sensor). 

See how the numbers pan out.

Only if you actually replace the sensor yourself and calibrate it yourself is it actually worth the effort to save some bucks. If not, you are better off buying a brand new unit. 

What Is Oxygen Detector Bump Testing?

• Bump testing is a procedure where the user exposes the detector to a small amount of “blast” target gas to ensure the detector operates as expected. 
• Since the target gas "oxygen" exists in the atmosphere, bump testing oxygen detectors is typically performed using pure nitrogen gas. 
• The function of this test is to verify proper operation and build user confidence, particularly in hazardous and critical user applications.
• It is recommended to bump test when first purchased, followed by weekly tests. Testing is critical in LIFE THREATENING and / or DANGEROUS applications in order to verify detector operation. See video explanation here. 

How Do I Take Care of My Oxygen Detector?

• Store your oxygen detector at normal room temperature - about 70F with 50%RH (well within operating specifications).
• Store it away from electromagnetic or magnetic sources, such as phones.
• Store it in a clean environment with no dust or particles.
• Store it away from any exhaust gas, concentrated vapors, or harsh chemicals that may poison the sensor.
• Clean the casing of your detector with a damp cloth.
• Store it in a stable place where there are no vibrations or continuous shaking.

How Do I Properly Use an Oxygen Detector?

When operating an oxygen detector, there are some tips to consider. Obviously, be smart and read your product manual. Be sure to keep these tips in mind:

• Ensure the oxygen detector has been bump tested and validated as operational. Check to make sure that it is reading 20.9% in fresh air. If it is 20.8% or 21.0%, that is OK. If it is fluctuating beyond that, give it a quick calibration to fresh air so it displays 20.9%.
• When using a personal protection oxygen detector, turn it ON, and keep it on your person. Set your alarms as desired.
• If performing analytical measurements, keep the unit stationary. Ensure humidity and temperature are also tracked and remain constant as possible.
• Recovery time (i.e. time to come back to 20.9%) is typically longer than the response time of the oxygen sensor.

What Is the Difference between ppm and % Oxygen Readings?

The typical scale of concentration for O2 is ppm or %.

In most cases, oxygen % is used more often because air has a known concentration of 20.9%. The parts per million (ppm) scale is used when low levels of oxygen may be present. In this case, it is easier to communicate in ppm than the % scale. For example, it is more clear to say 10 ppm than 0.001%. 

Conversion Example

O2 % value = (O2 ppm / 1,000,000) x 100%

For example, if we have 5,000 ppm of O2, then we obtain

O2 % value = (5,000 / 1,000,000) x 100%

O2 % value = 0.5%

Quick Conversion

10 ppm = 0.001%

100 ppm = 0.01%

1,000 ppm = 0.1%

10,000 ppm =1%

100,000 ppm =10%

1,000,000 ppm =100%

Final Words

Oxygen (O2) detectors are one of the most essential gas analyzers due to the necessity of oxygen for human life. These important safety devices alarm when oxygen levels drop significantly to help avoid occupational dangers. An oxygen detector is a handheld unit that instantaneously detects the O2 levels and displays it on the digital screen. In recent years, the price of oxygen detectors has dropped and can be purchased for less than $200.

About The Author Dr. Koz is the Chief Engineer of Forensics Detectors. 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