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Everything You Need To Know About Carbon Dioxide (CO2)

Dianna Smith

Carbon dioxide (CO2) levels are the highest they’ve been in almost three million years. During the past five decades, humans have added enough carbon dioxide to raise the global concentration of atmospheric carbon dioxide by about 100 ppm and growing. With some climate models predicting CO2 levels to rise to over 900 ppm by then of the century, many people are concerned about the effects of carbon dioxide on the climate.

However, it’s not just climate change we need to keep an eye on. Indoor carbon dioxide can also impact our health directly, and studies continue to draw connections between elevated levels of carbon dioxide, negative trends in cognitive performance, and difficulties sleeping.

This post will introduce what carbon dioxide(CO2) is and explore the relationship between indoor carbon dioxide and our health, as well as the connection between atmospheric carbon dioxide and climate change. Read more to find out what you need to know about CO2 and how to protect yourself.

Carbon Dioxide: Everything You Need to Know

  1. What is carbon dioxide (CO2)?
  2. Atmospheric CO2 and climate change
  3. Where does CO2 come from?
  4. How indoor CO2 directly impacts your health and well-being
  5. How to protect yourself from CO2
  6. Key points to remember

What is carbon dioxide (CO2)?

Carbon dioxide, known as CO2, is a naturally occurring gas in the atmosphere. Made up of one carbon atom and two oxygen atoms, carbon dioxide plays a critical role in the environment, the climate, and even your body.

Carbon dioxide is one of the main ingredients for photosynthesis, the process by which plants produce their own food from sunlight. Without carbon dioxide, plants would not be able to survive on Earth. Carbon dioxide also regulates your breathing and is a byproduct of respiration. When indoor carbon dioxide levels get too high, though, it can be detrimental to your mental abilities and wellness.

Similarly, carbon dioxide plays a significant role in maintaining a habitable climate on the planet. As a greenhouse gas, carbon dioxide traps heat in the atmosphere, keeping our planet warm even when the sun isn’t shining. Recent outdoor carbon dioxide levels, however, have skyrocketed due to anthropogenic CO2 emissions.

Atmospheric Carbon Dioxide and Climate Change

We can’t discuss carbon dioxide without bringing up the elephant in the room: climate change.

While there is some dispute about the reality of climate change, the overwhelming scientific information and consensus speak for themselves. Climate change is real, and it’s one of the most dangerous challenges we will face as a species. And as a major contributing factor, carbon dioxide emissions are a primary concern.

So, how does atmospheric CO2 impact the climate? Well, carbon dioxide is what’s known as a greenhouse gas (GHGs). According to the EPA, greenhouse gases are “gases that trap heat in the atmosphere.” Among other GHGs, like methane, nitrous oxides, and fluorinated gases, carbon dioxide retains less heat than the others. However, carbon dioxide accounts for around 82% of GHG emissions, so the sheer quantity of CO2 being released into the atmosphere by humans every year makes it one of the leading instigators of climate change.

Evidence of global warming has been building up for decades, and the connection between human emissions and atmospheric warming was hypothesized as early as the 1800s. And while much of the damage inflicted by climate change is incalculable, climate change poses a real threat to your health and the health of your loved ones.

Climate change may directly harm us through:

  1. Air-pollution-induced allergies and asthma
  2. Vector-borne diseases like malaria, dengue, and Lyme disease
  3. Malnutrition and starvation
  4. Poor water quality (i.e. cholera and algal blooms)
  5. Civil conflict and forced migration
  6. Heat-related illness
  7. Cardiovascular disease and stroke

Where Does CO2 Come From?

Because carbon dioxide is a fairly common atmospheric gas, it is produced by many natural and manmade sources.



Sources of Atmospheric CO2

Atmospheric carbon dioxide arises from a combination of natural and manmade sources. Nature tends to balance-out natural sources of carbon dioxide through the carbon cycle and carbon sinks, but human sources of outdoor carbon dioxide disrupted this delicate balance. Common anthropogenic sources of atmospheric carbon dioxide include:

  • Industrial processes, like refineries, chemical production, and cement
  • Electricity production, especially coal-fired power plants
  • Transportation, like cars, trucks, and planes

Sources of Indoor CO2

While all sources of CO2 ultimately end up in the atmosphere or ocean, there are specific emissions that impact us inside buildings. Here are a few sources we should keep in mind.

  1. Your body: One of the largest sources of indoor carbon dioxide is actually our bodies. As you breathe, each one of your body’s cells takes in oxygen to complete a process called cellular respiration. During this series of chemical reactions, your body produces carbon dioxide, which it releases it when you exhale. Typically this carbon dioxide would disperse into the air, but in closed rooms and homes the CO2 has nowhere to go.
  2. Poor ventilation: Many homes today are built to save energy. For this reason, they are tightly sealed and trap CO2, letting it build up to unhealthy levels.
  3. Home cooking: Any form of fire in your home will produce carbon dioxide. If you use a gas or wood stove, fireplace, smoke, or even burn candles in your home, you are producing CO2.

How Indoor CO2 Directly Impacts Your Health and Well-Being (Safe Levels of CO2)

Scientists used to believe that carbon dioxide was harmless at common indoor levels, but new findings indicate that this is not the case. From sluggish two o’clock meetings to poor sleep, elevated concentrations of indoor CO2 can directly impact our health and well-being in a number of ways.

The main way indoor carbon dioxide affects our health is through our brains. As carbon dioxide levels in a room increase, the gas starts crowding out the oxygen. Carbon dioxide is considered a simple asphyxiant because it reduces the amount of oxygen we absorb from each breath. If indoor carbon dioxide levels get too high (around 40,000 ppm), your life may be in danger.

At levels we are more likely to experience (1000-5000 ppm), the health effects are more subtle. Around 1000 ppm, a very common indoor level, you will start to experience fatigue, sleepiness, and may struggle to concentrate. You may also find it uncomfortable to sleep, and the air will feel stuffy. With prolonged exposure and increases in concentration, you may develop a headache and feel physically uncomfortable.

What levels of CO2 are safe?

  CO2 Concentration Health Effects
  <1000 ppm Limited or no health effects
  1000 ppm-2500 ppm Fatigue, loss of focus and concentration, uncomfortable ‘stuffy’ feeling in the air
  2500 ppm-5000 ppm Headache, drowsiness, tiredness
  5000 ppm-40000 ppm Violates OSHA requirements, severe headaches, slight intoxication depending on the exposure time
  40000 ppm-100000 ppm IDLH (Immediately dangerous to life or health), dizziness, increased heart rate, sweating, difficulty breathing; seizures and loss of consciousness after prolonged exposure
  >100000 ppm Loss of consciousness within minutes, coma, risk of death


Indoor carbon dioxide can also impact our decision-making and problem-solving skills. The Lawrence Berkeley National Laboratory uncovered a connection between carbon dioxide concentrations and cognitive and working ability. Most activities dipped slightly when exposed to 1000 ppm indoor CO2 levels, but the cognitive abilities across a spectrum of functions tanked at 2500 ppm. In fact, the reduction in cognitive functioning at 2500 ppm is comparable to the blood alcohol limit in most U.S. states.

Places that are particularly at risk of developing high indoor CO2 levels are: office meeting rooms, closed bedrooms, car interiors, school classrooms, kitchens, and home offices.

The connection between indoor CO2 and cognitive functioning is especially important for parents. The air in schools may not be as safe as we think. A study done in Texas revealed that most schools had carbon dioxide levels above 1000 ppm, and one in five had levels exceeding 3000 ppm. All this CO2 can inhibit your child’s school performance and wellness.

How To Protect Yourself From High CO2

As a colorless and odorless gas, indoor carbon dioxide is impossible to track on your own. Luckily, there are some simple steps and devices you can use to keep the gas below harmful levels. Here are five ways to protect yourself from indoor CO2:

  1. Ventilation is key - The best way to keep indoor CO2 at bay is to dilute it with fresh, outdoor air. If outdoor pollution levels are healthy and the room feels stuffy, open a window to release any excess carbon dioxide, when you’re cooking especially. Also, check to make sure your HVAC system is in working order.
  2. Measure your CO2 levels with a CO2 monitor - A monitor will help you recognize when carbon dioxide concentrations are high so you can take steps to reduce the impact of indoor CO2.
  3. No smoking - Smoking cigarettes release a tremendous amount of CO2 and other harmful chemicals. Make a rule that smoking is not allowed inside, or must be next to an open window.
  4. Cut down on lengthy work meetings - Have meetings in open areas, with the windows or door open to let out CO2. Limit the amount of time spent in cramped meeting rooms to keep everyone performing at the top of their game.

Key Points To Remember

Carbon dioxide packs a bigger punch than many people realize, and rising global concentrations of the gas will continue to be a huge concern moving forward. CO2 can harm us indirectly through climate change and directly through the air we breathe.

  1. CO2 is a GHG that contributes to climate change, which poses serious health risks
  2. High concentrations of CO2 cause headaches, drowsiness, and problems focusing
  3. The largest sources of indoor CO2 are exhalation, gas stoves, smoking, and fireplaces
  4. You should open a window, check your HVAC system, or open the door to vent CO2
  5. Holding shorter meetings, banning smoking, and getting a CO2 monitor will help protect you from CO2

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