Carbon Dioxide (CO2) Purity Grade Chart

One of the things we take pride in at CO2Meter is discussing new applications that our customers share with us. We always say “now we've heard it all. Then someone calls with a new application that amazes us all over again.

However, we are rarely asked about the difference between food, beverage, or medical grade CO2. Yet we've learned that, after buying hundreds of cylinders of CO2 for product testing over the years, the grade of CO2 is important.

That’s right – there are different grades or “purities” of CO2 that are produced and used.

Importance of CO2 Purity Grades

The purity of CO2 is important across various industrial, restaurant, medical, and scientific applications. This is because different grades of CO2 purity ensure that the gas meets specific requirements for its intended use.

The importance of using the correct CO2 purity grade also stems from its potential impact on the properties and characteristics of the materials or substances with which it interacts. Carbon dioxide is a widely used gas in various applications, such as analytical chemistry, environmental monitoring, and medical procedures. In these contexts, the purity of CO2 plays a critical role in ensuring accurate measurements, reliable data, and safe operations.

The presence of impurities, even in trace amounts, can cause interference or contamination, affecting the quality and reliability of the results. Furthermore, certain impurities may react with the materials or substances, causing undesirable changes or damage.

For example, industrial applications like welding utilize 99.5% pure CO2. In welding, higher purity CO2 produces better welds because the process is heating less impurities in the process. Those impurities have been found to produce less stable welds.

Here are some additional reasons why CO2 purity grades are so vital:

1. Industrial Applications: In industrial settings, CO2 is used for processes such as welding, food and beverage production, and chemical manufacturing. Impurities in CO2 can negatively impact the quality and safety of these processes. For example, impurities like moisture, hydrocarbons, or sulfur compounds can contaminate products or damage equipment.

2. Beverage Carbonation: In the food and beverage industry, CO2 is commonly used to carbonate beverages like soda and beer. The purity of CO2 is crucial to ensure the taste, quality, and consistency of the final product. Even small impurities can alter the flavor or appearance of beverages.

3. Medical Applications: In the medical field, CO2 is used in applications such as respiratory therapy, laparoscopy, and cryotherapy. High purity CO2 is essential to prevent contamination and ensure patient safety during medical procedures.

4. Analytical and Laboratory Use: In scientific research and laboratory settings, CO2 is often used as a carrier gas in chromatography and as a calibration gas for analytical instruments. Impurities in CO2 can interfere with analytical measurements, leading to inaccurate results.

To meet the specific requirements of different applications, various grades of CO2 purity are defined by organizations such as the Compressed Gas Association (CGA) in the United States or the European Industrial Gases Association (EIGA) in Europe. These grades specify maximum allowable impurity levels and other quality parameters to ensure that CO2 meets the necessary standards for its intended use.

Table: CO2 Purity Grades

GRADE	PURITY	OTHER GASES
Research	99.999%	0.001%
Super-critical Fluid	99.998%	0.002%
Laser	99.95%	0.05%
Anaerobic	99.95%	0.05%
Beverage	99.9%	0.1%
Food	99.9%	0.1%
Bone Dry	99.8%	0.2%
Medical	99.5%	0.5%
Industrial	99.5%	0.5%

The biggest difference between the grades are the amounts and kinds of impurities that are allowable in the CO2.  

As you ascend the list the amount of impurities like ammonia, benzene, oxygen, carbon monoxide, and others allowed to be in specific grades of gas are lessened. While nobody wants to ingest benzene or ammonia those hydrocarbons are far more dangerous when working with lasers than with lagers.

Does Beverage Grade CO2 Matter?

Specialty gases have become key components for almost every industry, including beverage, restaurant, scientific, incubation, agriculture, safety and others. The grade or "purity" of the gases can be influenced by elements such as oxygen, moisture content, total hydrocarbons, nitrogen, and carbon monoxide - to name a few.

In the U.S. specifically, beverage grade CO2 will almost always be at least 99.90% pure; many other molecules can compromise the other 0.10% (1,000 parts per million), including water, oxygen, and hydrocarbons such as benzene, acetaldehyde, and other molecules. 

Here are a few other helpful hints to ensure you are gaining the highest grade CO2 when looking at beverage application:

• For carbonated beverages, specify and use either ISBT Purity Grade beverage grade CO2 or Food-Grade CO2.
• Suppliers should provide a certificate of analysis (COA) upon delivery of CO2 to document that the actual lot meets the required purity specifications.
• Periodically audit the quality management practices of your CO2 supplier and request that they verify their quality through an independent ISO-certified lab.
• Ask your supplier what proportion of their CO2 supply derives from ethanol production, petrochemical production, or other sources (this may allow you to assess supply risk).
• Ask your supplier what steps they are taking to ensure that beverage grade CO2 quality and quantity requirements will be met in the event of supplier feedstock source changes.

Then ask yourself these simple questions:

1. Do you know what grade gas you are receiving from your gas supplier? 
2. Have you ever thought to ask them?
3. Is your gas supplier providing you with a certificate of purity?

Food Grade vs. Beverage Grade CO2

Food grade CO2 is tested to a different standard than beverage grade CO2. The standards and criteria for each grade of CO2 are established by both the United States Pharmacopeia (USP) and the Food and Drug Administration (FDA). For example, the USP sets specific purity standards for food grade CO2, which must meet stringent requirements to ensure that it is safe for use in food processing, storage, and transportation. These standards include limits on impurities, such as heavy metals, pesticides, and microbiological contaminants.

In the EU, food grade CO2 is regulated by the European Commission (EC) who states a minimum purity criteria for food grade gases such as CO2, N2 and O2.  Each having to adhere to a number code and must be of high purity.  

In contrast, beverage grade CO2 must meet specific standards established by the beverage industry to ensure that it does not contain any off-flavors, odors, or impurities that could affect the taste or appearance of the final product.

CO2 purity for beverage grade gases is now also mandated by the Food and Drug Administration. The FDA regulations allows for the other .09% of the gas to be made up of other hydrocarbons.

Therefore, while both food grade CO2 and beverage grade CO2 are high-purity gases, they are tested to different standards to meet the unique requirements of their intended applications.

When it comes to using medical grade carbon dioxide these applications typically encompass hospitals, scientific research, or laboratory discoveries. For instance, medical grade CO2 is used for:

• Respiratory therapy: used to facilitate breathing and treat respiratory conditions.
• Laparoscopic surgery: used to create a pneumoperitoneum, which inflates the abdominal cavity to provide a better view of the surgical site.
• Cryotherapy: used to freeze and destroy abnormal tissue, such as warts, moles, and tumors.
• Dental procedures: used to dry and isolate the treatment area, such as during root canal therapy or tooth extraction.
• Dermatology: used to treat various skin conditions, such as acne, rosacea, and wrinkles.
• Endoscopy: used to insufflate the gastrointestinal tract, providing a clearer view of the internal organs.
• Hyperbaric oxygen therapy: used to pressurize the chamber and deliver oxygen to patients with various medical conditions.

CO2 Purity Grade Tips

If you are unsure of your gas quality or call your suppliers analysis in to question you can contact an outside laboratory for third party testing services. You can contact airbornelabs.com as an example.

Also consider testing the water in your process as well. Brewers and vintners are keenly aware that water purity is just as important to end quality as the gas that they are using in your process. In fact, hydrocarbons like benzene are more likely to appear in the water in your process then in the gas you are using.          

If you are interested in further details about beverage gas and its chemical composition please visit the International Society of Beverage Technologist, which CO2Meter, Inc. is a member of, at bevtech.org.

Carbon dioxide has become such an integral part of many industries and applications. Understanding the importance of gas purity, trace-ability in its use, and specific regulation/standards is crucial. 

For more information on other gas purity grade charts like oxygen, click here.

Protect Yourself and Your Establishment from CO2 Over Exposure

If you are using or storing more than 100 lbs of CO2, a Fixed Industrial CO2 Safety monitor is critical to protecting your establishment and employees from a potential co2 exposure incident. 

Industrial fixed gas detectors offer numerous benefits, particularly in environments where the presence of hazardous gases could pose a significant risk to safety and operations. Key advantages can include but are not limited to, automated alerts, wireless cloud capabilities, control of third-party systems, and enhanced worker and facility safety.