CO2 Sensor Range: PPM and Percentage Compared

September 10, 2024

Understanding carbon dioxide ppm range

Knowing the CO2 sensor range you need in parts per million (ppm) or percentage CO2 is the first step in selecting the right carbon dioxide sensor or monitor.

One of the most common questions we receive at CO2Meter is "Which CO2 monitor (or sensor) is best for my application?" This is a great question, because every application uses a different CO2 range.

In fact, carbon dioxide monitors are offered in a variety of ranges from a few parts per billion to 100% CO2 by volume. Selecting the sensor or monitor with the correct range of CO2 is important because the narrower the range of CO2 levels measured, the more accurate the sensor or device will be.

For example, a 200 ppm change will be seen on a 2,000 ppm CO2 sensor, but not on a 100% CO2 sensor. On the other hand, a 5% change in CO2 levels can't be viewed on a 2,000 ppm CO2 sensor.

So before we can talk about applications, it helps to understand the differences between CO2 sensor ranges from parts per million to percent CO2.

Parts per million (ppm) vs. Percent CO2

It's important to know the difference between parts per million and percent CO2.

Carbon dioxide is considered a trace gas in the atmosphere.

Suppose you had a box of dry, outdoor air with 1 million molecules of gas in it. If you could count every molecules by hand, here are the piles you'd make:

780,840 molecules of nitrogen (78.08%)
209,460 molecules of oxygen (20.9%)
93,400 molecules of argon (0.93%)
500 molecules of hydrogen, helium, methane, others
400 molecules of carbon dioxide

As you can see, once you get past counting the number of nitrogen, oxygen and argon molecules, the number of molecules of the remaining gases in our theoretical box of air is very small.

For this reason gases with over 1% by volume are measured as a percent. For smaller volumes, sensor manufacturers and the gas industry measure CO2 and other trace gases in parts per million. For example, 0.04% CO2 is equal to 400 parts per million, which is commonly abbreviated as "400 ppm".

Learn how to measure CO2 accurately.

CO2 Sensor Ranges by Industry

In general, CO2 sensors, monitors, meters and analyzers can be divided into 3 groups:

0 - 10,000 ppm for indoor air quality (IAQ)
50,000 ppm - 5% for personal safety, restaurants, beverage, indoor agriculture, and life sciences
5% - 100% for industrial, fire suppression testing, biological

Selecting the proper CO2 range for your application makes it easier to choose from our list of available CO2 sensors and products. It also ensures you'll have the most accurate sensor for your application .

Here are some examples of applications and industries where different CO2 sensor ranges are used.

Indoor Air Quality: 400 - 10,000 ppm CO2

When talking about indoor air quality (IAQ) parts per million of CO2 makes sense. Only in rare instances like being in a cave or near an active volcano would you ever be exposed to CO2 levels above 1% (10,000 ppm) in nature.

That's why for IAQ for homes, schools, or office applications, a 2,000 ppm to 10,000 ppm CO2 sensor or monitor is the right choice. Fresh air contains approximately 400 ppm CO2. The ASHRAE Standard for ambient indoor air in occupied spaces has changed over the years but in general they recommend between 800-1,000 ppm.

Therefore, an indoor air quality monitor or sensor that measures at these levels and can indicate to individuals should the threshold exceed the standard; will be the most accurate for indoor air quality applications.

The most popular sensors we sell in this range are the K30 CO2 Sensor by Senseair and the COZIR Ambient CO2 sensor. These sensors are used worldwide by OEM manufacturers of indoor air quality devices. They are also used in outdoor air quality devices to monitor CO2 levels.

See our line of indoor air quality monitors.

A 10,000 ppm CO2 sensor is also a good choice for air quality verification in car parks or garages that must meet OSHA specifications. The Occupational Safety and Health Administration guidelines for confined spaces require that the time-weighted average (TWA) over an 8-hour workday for a garage employee should not exceed 5,000ppm.

Personal Safety - 5% CO2

CO2Meter Beverage Product Portfolio

For CO2 safety applications where workers or the public are around tanks or cylinders of stored carbon dioxide, a 5% CO2 sensor or device is the best choice. A CO2 leak in an enclosed area can be fatal. If a CO2 tank or cylinder leaks, these sensors can be used to set off an alarm. 5% CO2 sensors and devices meet all OSHA, NIOSH, NFPA, IFC, and NBIC Requirements.

For example, our CO2 Storage Safety 3 Alarm is widely popular and meets all code requirements. For a hand-held portable device, these personal CO2 alarms use a 5% CO2 sensor.

These devices can all be used in applications such as restaurants, fast-food establishments, breweries, wineries, or cultivation facilities who are looking to ensure compliance and meet personal safety CO2 monitoring regulations per their jurisdiction.

Industrial Processes - 5% CO2

In industrial processes for example, carbon dioxide (CO2) is used in metalworking processes, such as in welding and as a shielding gas. The usage in this industry is relatively small, contributing to about 3-5% of total industrial CO2 consumption. Outside of metalworking and welding, CO2 is also used in enhanced oil recovery, where it is injected into oil reservoirs to increase the extraction of crude oil. This application accounts for a significant portion of CO2 usage, with estimates suggesting that about 40-60% of industrial CO2 use is dedicated to EOR.

For industrial processes using carbon dioxide in high concentrations, in order to protect personnel and facilities the use of an industrial fixed carbon dioxide gas detector or controller is critical.

These devices can all be used not only to protect personnel but to provide instant audible/visual indication should a potential leak be present and to ensure compliance with CO2 specific safety regulations and standards.

Biological Processes - 100% CO2

For industrial and biological processes like wood gasification or biological incubators where higher levels of CO2 are required, a 10-100% CO2 sensor or device is the best solution. For example, our SenseAir K33 ICB or GSS Wide-Range sensors are in this range. In addition, the high-speed CM-1000 Multi Sampling Data Logger is an excellent choice for incubation or industrial scientific applications.

For applications like controlled atmosphere storage for grains that require the ability to measure up to 100% CO2, we recommend the SprintIR GC-0018 CO2 sensors.

Another example is the MH-100 Biological Incubator CO2 Sensor. It is designed to monitor carbon dioxide levels in cell incubators to manage ideal cell and tissue growth, typically at 5% CO2.

Other CO2 Sensor Applications

Here are a few more examples of use cases for carbon dioxide monitoring:

Less than 10,000 ppm

1-5% CO2

5-100% CO2

With all the different emerging applications compared to products we offer, it might seem confusing as to which one is best for your particular use. However, by understanding the proper CO2 range required, you can narrow down the list of sensors or products significantly in order to choose the right device for you.

Furthermore, for someone to become well-versed on CO2, it is also important to remain knowledgeable of current regulations, industry applications, signs of exposure, device use and analysis, and how to explain the dangers to others.

Of course, a CO2Meter sensing expert can always assist if you have any questions. Give us a call or contact us for more information.

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Tags: Sensor

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