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Is Carbon Dioxide Directly Harmful to People?

You may have heard about CO2 on the Internet or by watching the news; there is a lot of concern about carbon dioxide’s effect on the atmosphere. Carbon dioxide is a significant greenhouse gas that contributes to climate change.

While this is worrying, many people are also concerned about the effect that CO2 has on human beings. Now we have the question: Can CO2 directly harm you?



Short Answer: Yes. At certain concentrations, CO2 can harm you.

Long Answer: Yes, but it is more complicated. We used to think that CO2 could only harm people at unrealistic concentrations, but this answer has started to change. To understand why this is, let’s first talk about what CO2 is and how it relates to humans.


What Is CO2?

Carbon dioxide, also called CO2, is a colorless, odorless gas. You may have also seen carbon dioxide in its solid form through dry ice. As CO2 heats up, it goes right from solid to gas, so you can’t see liquid carbon dioxide.

Carbon dioxide is very small, with only one carbon atom and two oxygen atoms forming the whole molecule. Even though carbon dioxide is a common gas, it makes up less than 1% of the atmosphere. Outdoor CO2 levels average around 400 ppm, the highest it has been in thousands of years. The levels indoors can increase far beyond that, upwards of 1000 ppm or even 2000 ppm.


Where Does CO2 Come From?

When talking about indoor CO2 levels, the main culprit is actually your body. As you breathe, your body takes in oxygen and releases carbon dioxide. This released CO2 increases the concentration of CO2 in a closed room. Other sources of CO2 in a room include smoking, cooking using a gas or wood stove, and using fireplaces. Any open flame in your home is creating CO2.


You don’t usually have to worry about carbon dioxide when outdoors because CO2 emissions get diluted by the surrounding air. However, if you are in an area with exposure to fire or combustion, whether natural or man-made, CO2 levels in that area may become dangerously high.


Effects of CO2 on the Body

CO2 is not poisonous; as a gas, CO2 itself will not hurt you. In fact, you breathe it in every day without any ill effects. It’s only when CO2 gets concentrated do you have to worry.

Carbon dioxide acts as a simple asphyxiant; in other words, as CO2 levels in a closed room rise, carbon dioxide replaces the oxygen your body needs. When your body can’t get oxygen, it slows down and does not function properly.

Because carbon dioxide is an asphyxiant, it mostly affects your brain. At moderate CO2 levels, around 1000 ppm, there are observable effects on your thinking. These same levels also reduce concentration and focus, as well as create discomfort from breathing stuffy air. Overall, moderate levels of CO2, which are very common in office meeting rooms, schools, and even your home, won’t let your body function optimally.

At higher levels, around 2500 ppm, there are substantial reductions in cognitive functioning, especially for tasks that require higher-level thinking. People feel fatigued and report having more headaches. These conditions are less common but can still occur regularly in schools and poorly ventilated buildings. The chart below summarizes a study that shows how CO2 affects your brain functioning.

Screenshot 2019-07-04 at 10.08.29 AM

If CO2 levels get severe (>50,000 ppm), it can also cause you to lose consciousness. If this occurs for long enough, death is a possibility. However, these conditions are unrealistic; you would only encounter these conditions in exceptional circumstances, such as a leaky basement over an abandoned coal mine.

While these conditions are rare, CO2 levels over 1000 ppm can directly impact you, draining your concentration and energy levels. Luckily, there are a few ways you can prevent CO2 levels from getting this high in your home. Click here to find out how you can breathe fresher air.


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