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Oxygen Purity Grade Chart

industrial specialty oxygen gas

When we look at the many ways customers use oxygen in everyday applications, the uses cases are endless. From hospitals, laboratories, food production, fabrication, industrial manufacturing and even cryospas - these customers all find oxygen gas paramount in their process.

There are also several ways that industry professionals get their oxygen supply and this oxygen comes in different grades. 

While we are used to hearing common customer questions such as “What should my oxygen concentration be?” or “Am I using the right oxygen monitor?" the one topic that tends to be overlooked, but is critical is the purity of the gas itself. 

To get pure oxygen, oxygen plants must employ a specialized technique to separate the oxygen from the air and this is often by collecting air in gaseous form and liquefying it at cold temperatures.

Once this gas is collected, it must be inspected, sometimes regulated, and packaged into two unique grades. The Compressed Gas Association (CGA) has identified seven grades of oxygen, to determine how pure the gas actually is.

Almost all oxygen production facilities now also meet specific requirements due to economic reasons of storing gas in facilities, but the purity of the gas and the way it is filled is critical. Below, we talk about the most common oxygen purity grades which are medical oxygen and industrial oxygen.

Industrial Grade vs. Medical Grade Oxygen

While oxygen gas is critical for us humans to breathe and live each day, you may be surprised to find that their are different types of oxygen. In fact, there are two main types of oxygen gases: medical oxygen and industrial oxygen.

While they both are integral to specific industries they also pose unique differentiators and it's important that customers know what type of gas they are buying to ensure it fits their needs, requirements, and environment.

When you think of medical vs. industrial oxygen one should think of medical oxygen as more of a necessity to maintain good health and industrial conversely, as a necessity to maintain industrial function. 

The last key difference between both gases is the way that it is regulated. While medical oxygen has strict parameters set by the FDA, industrial oxygen is not regulated as strictly which allows a greater chance for contamination. Further, making the use of industrial oxygen in a medical environment - dangerous.

Medical Grade Oxygen

When we look at medical oxygen we know that it is essential for caring for individuals and especially vital for patients in the healthcare system. Oxygen is critical for many hospital treatments like surgeries, trauma, heart failure, asthma, pregnancy, and pneumonia. 

If you have a chronic disease you may need additional medical oxygen for your organs to function normally and the grade of oxygen you are receiving should be one that is fundamentally clean from any impurities.

As with any medication or treatment, medical oxygen must meet specific requirements to ensure safety and proper purity standards. In fact, medical grade oxygen is actually considered pharmaceutical and is classified as a "drug" meeting specific standards for medical use only.

Here are some helpful hints to ensure you are gaining "medical grade" oxygen:

  • For starters, medical oxygen can only be generated by medical air compressors.
  • The FDA regulates medical oxygen and sets strict parameters as it pertains to cleanliness and elimination of harmful contaminants.
  • Ask your supplier to verify their quality through an independent ISO-certified lab.
  • If you are gaining medical oxygen you should be required to visit your primary care physician to gain a prescription and/or have necessary documentation.
  • A chain of custody is required to verify that the cylinder is only being used for medical oxygen and safeguard against any contamination that could have taken place.

All in all, medical grade oxygen is only designed to be used and regulated specifically for patients demonstrating a medical need. For all other instances, see "industrial oxygen". 

Industrial Grade Oxygen

Those industries that use industrial oxygen typically include areas of combustion, oxidation, cutting, processing, and chemical plants. Chance are if you are doing any of the following you will need industrial oxygen:

  • Fabrication, welding, cutting, and cleaning
  • Steel cutting and manufacturing
  • Chemical process plant production
  • Paper-based manufacturing and bleaching
  • Bio-reaction processes

Here are some helpful hints to ensure you are gaining the "industrial grade" Oxygen:

  • Industrial grade oxygen is not regulated by the FDA
  • Industrial grade oxygen typically is full of impurities and you should ask your supplier to confirm this for your industrial setting.
  • Ask your supplier to verify their quality through an independent ISO-certified lab.

Now, let's take a look at O2 Purity Grades vs. Application

Oxygen Purity Grade Chart

Oxygen Purity Grade Concentration Maximum Contaminants
Research Grade > 99.999% Water < 1 ppm
Total Hydrocarbons (like CH4) < 0.5 ppm
Nitrogen < 4 ppm
Argon < 4 ppm
Carbon Dioxide < 1 ppm
Carbon Monoxide < 1 ppm
Ultra High Purity Grade > 99.994% Water < 1 ppm
Total Hydrocarbons (like CH4) < 0.5 ppm
Nitrogen < 10 ppm
Nitrogen < 100 ppm
Argon < 35 ppm
Carbon Dioxide < 1 ppm
Carbon Monoxide < 1 ppm
High Purity Grade > 99.8% Water < 5 ppm
Total Hydrocarbons (like CH4) < 50 ppm
Nitrogen < 100 ppm
Carbon Dioxide < 10 ppm
Carbon Monoxide < 1 ppm
Zero Grade > 99.6% Total Hydrocarbons (like CH4) < 0.5 ppm
Industrial Grade > 99.5% Water < 50 ppm
Aviator Breathing Grade > 99.0% Water < 6.6 ppm
Identity: Positive
Odor: None
Food Grade > 99.0% Identity: Positive
Odor: None
Medical Oxygen: USP Grade > 99.0% Odor: None
Identification: Positive
Carbon Dioxide < 0.03% (300 ppm)
Carbon Monoxide < 0.001% (10 ppm)


Click here to download the chart to print

In terms of cryogenic fields, many industries require a high 99.5% minimum requirement for oxygen purity but not PSA. Pharmaceutical companies also require Oxygen purity specifics for not less than 90.0% but not more than 96.0% for PSA oxygen. 

What is a dangerously low oxygen level?

The Occupational Safety and Health Administration (OSHA) Respiratory Protection Standard ("the Standard"; 29 CFR 1910.134) uses 19.5% oxygen as the level below which an oxygen-deficient atmosphere exists and requires, generally, that all oxygen-deficient atmospheres be considered immediately dangerous to life or health ("oxygen-deficient IDLH").

For example, normal ambient air contains an oxygen concentration of 20.9% oxygen by volume. When the oxygen level dips below 19.5% air is considered oxygen-deficient.

In addition, OSHA defines "oxygen enriched" atmospheres as any atmosphere that contains more than 22% oxygen.

Oxygen Gas Supply and Recommendations

Because oxygen is so vital it also is complex at times. Access to oxygen continues to meet many challenges surrounding availability, quality, affordability, supply, human resources, and safety. 

Because of these common hurdles, organizations like WHO continuously provide resources to overcome them and can be found here as a helpful reference.

No matter what your business or application is you should always contact your gas supplier and ask the following questions:

  • What grade/purity gas are you delivering to me?
  • Can you provide me with a certificate that states the purity?

Any qualified gas provider will be able to not only answer those questions immediately but they should also be able to demonstrate the gas quality as well. Do not settle for purity any less than what your application calls for.

In addition, you should always consider the main differentiators:

  • Medical oxygen is used to maintain healthy oxygen levels and is FDA regulated for impurities and contaminants. 
  • Industrial oxygen is used to support industrial functions and does not need regulation or concern with impurities in the gas.

Oxygen Safety Monitors

oxygen safety meter

Regardless of what grade O2 you use, in order to test the accuracy of a oxygen safety monitor, detector, sensor or alarm, you should purchase a gas monitor that meets oxygen specific levels and requirements.

The RAD-0002-ZR Oxygen Deficiency Alarm does just that as well as protect individuals when working in hazardous areas where nitrogen, helium, or argon could pose severe personal injury. 


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