CO2 vs. CO? What's so important when choosing a Gas Monitor?

In our ever-advancing world, it becomes increasingly important to understand the basics of the environment around us. Just like in education, the building blocks are critical.

In the gas detection and analysis industry, understanding the gases you are measuring is even more important because of the difficulties associated with measuring individual gases. The most important delineation we must make with customers is the difference between Carbon Dioxide (CO2) and Carbon Monoxide (CO).

Many people believe the two gases to be the same thing and often are confused because both are advertised as “silent killers". Some simply have an issue because you say "carbon" and they don't let you finish the statement to know if you mean "monoxide or dioxide".

While CO2 and CO have some similarities like their hazardous nature and the fact that both are odorless, colorless, and tasteless, understanding their differences is critical in selecting the proper sensing solution.

Let's Talk Gases

Our starting point will be "how the gases are produced".

CO2 is a naturally occurring gas in the earth's atmosphere and is normally measured at approximately 400 ppm (parts per million).

CO2 forms naturally in the atmosphere from the decomposition of organic and animal matter, geothermic activity, and human processes like the burning of fossil fuels and fermentation.

CO is almost entirely a man-made gas that is not normally found in the earth's atmosphere. You will find that CO occurs most often due to the incomplete combustion of fossil fuels like gasoline, oil, and coal.

While both can be found in industrial settings, the workplace, or even at home, knowing where concentrations or leakages could occur is very important to one’s overall health and safety.


CO can be a flammable gas in higher concentrations (sometimes referred to as C1D1 or C2D2 environments) and devices to measure carbon monoxide in these concentrations are normally designed to be explosion-proof.

CO2 on the other hand is a non-flammable, inert gas with no explosive properties.

Deadly Concentrations

Another common misconception is that the concentration at which CO and CO2 are deadly is identical. However, nothing could be further from the truth.

OSHA lists danger levels for CO beginning at 35 ppm, and for CO2 starting at a 5,000 ppm time-weighted average.  Those are vastly different levels.

Therefore, there is a need for separate sensing technologies and monitoring devices in order to detect them individually.

This is also why carbon monoxide safety alarms or sensors can not be used to measure carbon dioxide concentrations and vice versa. 

Now would you be able to understand which gas to detect and properly monitor in your industry, environment, or application?

CO & CO2 Applications

Typical CO emissions are found near cars, freeways, in-service/repair shops, parking garages, and near gas-fired furnaces and boilers.

Common CO2 emissions are found in restaurants, breweries, greenhouses, modified atmosphere packaging, indoor air quality, welding applications, and industrial off-gassing.

Because CO2 and CO are commonly lumped together this is why many people believe you can monitor both gases together. This is not only a false statement it is a dangerous misnomer as well.

The Carbon Monoxide molecular weight is 28.01, meaning that you will find the gas somewhere between the middle to the top of a room.

The Carbon Dioxide molecule on the other hand has a molecular weight of 44.1 meaning that you will find the gas collecting near the floor. 

Sensors need to be mounted at the appropriate heights to do their work.

These misnomers also lead to the common misconception that you can buy an accurate CO and CO2 monitor at your local hardware or big box store AND that you can mount them together.

While we'd love to have Lowe's or Home Depot carry our devices (call our sales team if you have a contact at either) they do not offer CO2 monitors and only sell the most basic of CO detectors to keep your home "safe". Note, that CO detectors purchased at retail have a limited life span and should be tested multiple times per year to ensure operation.

Since CO is a lighter gas than air, when choosing a Fixed Wall Mount Device these devices need to be placed towards the ceiling in order to properly detect harmful CO levels.

View the CM-503 Personal CO Handheld Detector

CM-503 - Carbon Monoxide (CO) Handheld Gas Detector

Portable CO detectors are also available if spot-checking spaces in facilities for harmful gas levels are needed. Our Portable Devices will offer the ability to detect single or multiple gases, are rechargeable, and will data log all the detected information.

Portable devices are particularly effective when utilizing portable power generating devices and heavy machinery. Combustion engines running in a confined space can be deadly.  Incidents with cars and tractors are well-publicized. So are incidents involving fatalities when generators are run inside homes during natural disasters like hurricanes.

View the CM-7000 CO2 Multi Sensor System for Restaurants, Breweries, Agriculture and Safety Industries

CM-7000 - CO2 Multi-Sensor System

Carbon Dioxide gas is in fact heavier than air and tends to collect at the floor or in low lying areas first. CO2 sensors such as in the CM-7000 CO2 Multi-Sensor System should always be placed 12-18 inches above the floor - to detect increased levels and to ensure safety!

One critical final factor is understanding and educating yourself, your families, and your employees about the symptoms for both gases to arm yourself in the event of an emergency.

Typical symptoms of CO2 exposure include decreased focus, cotton/dry mouth, disorientation, narrowed field of vision, increased heart rate, sweating, fatigue, muscle tremors, and shortness of breath.

CO exposure symptoms include: headache, dizziness, weakness, upset stomach, vomiting, chest pain, and confusion.

Regardless of whether you work in any of the industries mentioned above, leaks and overexposure to these gases can occur around you each and every day.  Recently publicized fatalities involving both CO2 and CO have refocused attention on the need to accurately and effectively detect and monitor for the presence of gases.

Understanding the gases and being able to prevent potential injuries and hazards from occurring is the best preventive first step you can take.

What are you waiting for?

For more information on CO2 and CO Safety Monitors speak to an expert today by calling (877) 678-4259 or by emailing

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