top of page

Carbon Monoxide Vs Carbon Dioxide 

Carbon Monoxide

Carbon dioxide (CO2) and carbon monoxide (CO). They kind of sound similar, don’t they? They both have "carbon", and they both have the same abbreviation, except one has a “2” at the end. They're both gases, but the two are completely different from each other. It’s important to know the difference between them, as it could potentially save your life.

About Carbon Dioxide (CO2)

Carbon dioxide is a colorless and odorless gas. The word “dioxide” comes from the Greek prefix “di”, which means “two”. It consists of one carbon compound and two oxygen compounds. That’s why there is a “2” after the "O" in its molecular formula: CO2. Carbon dioxide is a natural gas. We create it every time we breathe, and it plays an important role in the carbon cycle, making photosynthesis possible. Without it, life would be unsustainable.

Carbon dioxide is good for us. It keeps all living thing alive, including us, and even has a large variety of unique applications. It’s seen many times in the world of entertainment, and even has its place in the medical field. So with that in mind, how does carbon monoxide compare? 

About Carbon Monoxide (CO)

Carbon monoxide is a colorless and odorless gas, just like carbon dioxide. The word monoxide comes from the Greek prefix “mono,” meaning “one”. It consists of only one oxygen atom and one carbon atom, hence its molecular formula: CO. It results from badly ventilated fuel-burning appliances. Cars, gas ovens, and gas water heaters dispel CO for example, but they are typically safe as long as there's good ventilation.

Carbon monoxide doesn’t have any natural uses, only industrial applications. It mostly serves as a means of manufacturing metals. It reacts to specific metals like iron, cobalt, and nickel to form carbonyl compounds, which play a role in manufacturing plastic. It also is used in industrial heating and fuel mixtures. This means car fuel contains carbon monoxide. While carbon monoxide has no color or odor, it can blend in with other burned gases. This is why people immediately think of this gas when they see and smell those black smoke clouds from cars. Many appliances and products you can find in a supermarket are capable of producing carbon monoxide, like generators and charcoal grills. Manufacturing companies will warn people, by law, to use those product outside, and for good reason too.

Carbon Monoxide is commonly known as “the silent killer” due to it being a harmful gas that you technically can’t see or smell. It can severely damage your lungs, blood, and nervous system. It displaces oxygen from your blood causing air hunger, a feeling where you can’t take in enough air. It's capable of killing you faster than most other gases would. 

And of course, it's extremely flammable too. Lighting a match near it will create fatal consequences.

Carbon Monoxide Poisoning

Like carbon dioxide, you want to avoid taking in too much carbon monoxide. When too much of this gas is present indoors, carbon monoxide poisoning occurs. This is much worse than what excessive carbon dioxide is capable of. While the human side effects of excessive carbon dioxide can be alleviated, carbon monoxide poisoning can easily lead to chronic complications, with heavy emphasis on the word chronic. Brain damage and heart failure is an especially common side effect. Because these side effects will end up chronic, the damage can stay permanent and typically will get worse overtime, even when you’ve cleared yourself from excessive amounts of CO.

Tissue hypoxia is even common. As the gas starts displacing oxygen, it starts attacking your hemoglobin. This becomes a problem for your body carrying oxygen in the blood. It damages your lungs, hurts your breathing rhythm, and makes it difficult to consistently release oxygen. It's also capable of coloring your fingertips slightly blue.

Safe Pressure Levels

There’s a drastic difference in safe pressure levels when comparing carbon dioxide and carbon monoxide. You can survive CO2 pressures up to 350-1,000 ppm (parts per million) indoors. Going beyond that range could result in some questionable side effects. The least threatening one would be a slight case of drowsiness. High CO2 pressure isn’t ideal, but a moderate amount is safe. After all, it’s a natural gas that keeps us alive. Carbon monoxide, on the other hand, isn't natural at all.


The recommended CO pressure levels are extraordinarily low. According to ASHRAE and OSHA standards, 9-35 ppm would be safe for long term exposure of about 8 hours. This pressure range is also acceptable from within a safe work environment with good ventilation. As an example, your local hardware stores have some CO in the air due to industrial trucks driving inside the store. Most of the overstock products are on pallets, which rest above store shelves. The power equipment, from pallet jacks to forklift trucks, can move the heavy overstock pallets with ease. Yeah, they dispel some CO, but its nothing to worry about because, again, the CO pressure from within the store is still very low. Safety precautions prevent customers and even employees from getting too close to the equipment from the get-go, and the indoor space is usually large and very well ventilated. No need to worry about CO poisoning from inside the store, even if you're shopping for hours.

For short term usage, less than 3 hours, 800 ppm is acceptable. It's really not okay to go anywhere above those levels, but if you're in areas with pressures above 2,000 ppm, you’ll likely start experiencing common side effects before the CO poisoning itself begins to kick in. This is why the utilization of equipment producing this gas typically is done outside. Unless you're given legal approval, never under any circumstances should they be operated indoors or in small spaces.

So as you can tell, the differences are like night and day. Although carbon monoxide is toxic, low intakes in well-ventilated spaces can be safe. Just don't overdo it. Same thing goes for carbon dioxide. CO2 will keep us alive, but too much or too little of it can be detrimental to your health. If you feel like you're running out of air, we recommend stepping outside for some fresh air. It'll save your life and feel refreshing too. Calling poison control for additional help would be good too.

Explore more about Gas Safety

Image by Ash from Modern Afflatus

Gas Cylinder 
Laws & Regulations

Resources Series

Propane Safety Inspection.jpeg

Gas Cylinder Safety:
Good & Bad Tips To Remember

Blog Post

Image by Carolina Heza

The Side Effects Of Gas Leaks and Misusing Gas Tanks
Blog Post

How Can You Detect Gas Leaks Before They Happen?
Blog Post

Gas Cylinders on the Floor.jpg

Food Grade Vs Industrial Grade: Do The Differences Matter?
Blog Post

bottom of page