CO2 Tolerance: Why It's Important + 9 Ways to Increase Yours

Science
October 17, 2021

For many years, people have been conditioned to believe that carbon dioxide is bad for the body. While they tend to prioritize breathing exercises that help increase oxygen intake and strengthen the lungs, there are actually many benefits to gain from increasing CO2 tolerance.

If you’re curious to know how increasing your CO2 tolerance can help you, this article covers all of the following topics:

  • What is CO2 tolerance and why is it important?
  • 6 benefits of CO2 tolerance
  • CO2 test: try this simple test now
  • Basics of CO2 tolerance training
  • 9 ways to increase your CO2 tolerance
  • 4 resources to learn more about CO2 tolerance

Let’s start by covering what exactly CO2 tolerance is and why it can actually be good for you.

If you’re also wondering if breathwork is safe, check out this guide to learn everything you need to know.

What is CO2 tolerance and why is it important?

A group of people swimming in an outdoor pool

Carbon dioxide tolerance is the body’s ability to handle a temporary imbalance of CO2 and oxygen. The higher your tolerance is, the longer you’ll be able to hold your breath. Like breathwork, training to increase CO2 tolerance has gained popularity for its ability to improve physical and mental health.

It’s true that having a large amount of CO2 in the body is poisonous. However, having a small amount is both essential and beneficial, as it notifies the brain of the need to breathe. However, by increasing your CO2 tolerance, you can temporarily hold your breath for longer and maintain slow, deep breathing during periods of high stress while avoiding hyperventilation. We’ll discuss examples of benefits of this in the following section.

6 benefits of CO2 tolerance

Besides the obvious, there are many specific benefits of building up your tolerance. Below are some of the things that it can help with.

1. Helps reduce anxiety

Three people sitting on rocks while relaxing

One of the biggest issues triggered by shallow breathing is anxiety. Since CO2 is able to help maintain a consistent breathing pattern, having a higher tolerance can actually help reduce anxiety. Research conducted by HHP-Foundation found that those with a higher CO2 tolerance had lower in-the-moment anxiety. This suggests that building up your CO2 tolerance for anxiety can help you maintain a sense of calm during everyday life.

2. Helps you run faster for longer

CO2 tolerance and running are a winning combination, since the former has been proven to be beneficial for endurance athletes. This is because the more CO2 they can tolerate, the slower their heart rates will remain. Running with a low tolerance causes the heart to beat quickly, which will lead to feeling winded faster. Being able to tolerate more carbon dioxide means that your heart will continue to beat slowly, allowing you to increase your pace for a longer period of time.

3. Helps you stay underwater when freediving

Freediving can be an adventurous experience, but the need to breathe can shorten the amount of time someone can stay underwater. Building up your tolerance to carbon dioxide will help you to hold your breath for longer, meaning you can stay underwater for a longer period of time before needing to resurface to breathe. This is why CO2 tolerance training has become a key practice for freedivers.

4. Helps manage symptoms of depression

A group of people sitting on rocks in a forest while bonding

In addition to reducing anxiety, having a higher tolerance has been proven to help manage symptoms of depression. Carbon dioxide is able to calm the nervous system, allowing one to maintain a relaxed state and experience more positive emotions. This helps those experiencing depression work towards improving their mood.

5. Helps reduce inflammation

CO2 is also great at reducing inflammation throughout the body. Building a higher tolerance allows you to hold onto carbon dioxide for longer. This means that there’s more of it available to travel throughout your body and help relieve the inflammation.

6. Helps increase energy

Being able to tolerate CO2 can also help you produce more physical and mental energy. As you retain more CO2, it helps the mitochondria in your cells to multiply, which increases the amount of energy you have to burn off. This is great for anyone with an active lifestyle or who regularly needs to focus intensely on their work.

Try this simple CO2 test now

If you’re curious to know how well you currently tolerate CO2, there is a simple test you can take. Follow the steps for the CO2 Tolerance Test below and compare yourself to the results that follow.

How to implement the CO2 test

  1. Have a timer nearby and ready to use.
  2. Inhale and exhale normally 3 times through your nose.
  3. Inhale a 4th time, fully filling your lungs.
  4. When you’re ready to exhale, start the timer.
  5. Exhale slowly through your nose for as long as you can.
  6. Once you’ve run out of air, stop the timer.
  7. If you accidentally hold your breath or swallow while exhaling, you will need to stop the timer as you’ve stopped exhaling properly.
  8. Record your time and compare it to the results below.

Understanding the results

>80 seconds: Elite – an advanced pulmonary adaptation with excellent breathing control and stress control.

60-80 seconds: Advanced – a healthy pulmonary system with good breathing control and fairly good stress control.

40-60 seconds: Intermediate – likelihood of improving quickly with additional tolerance training.

20-40 seconds: Average – experiencing moderate to high stress/anxiety state; breathing pattern needs to be improved.

<20 seconds: Poor – very high levels of anxiety and stress sensitivity with poor pulmonary capacity and a possibility of mechanical restriction.

Basics of CO2 tolerance training

A woman smiling while lying in water

If your current level of tolerance has you wanting to improve, carbon dioxide tolerance training is an option. Here is everything you need to know about how to make use of tolerance training.

What it is and how it works

Carbon dioxide tolerance training involves the use of different techniques that gradually increase one’s ability to hold their breath for longer periods of time. For beginners, it’s best to focus on static apnea training, which is the simplest method and provides quick results for those who are dedicated to training. This is done through the use of static tables, which we’ll explain below.

As a precaution, please practice your training with others nearby in case you begin to experience hypoxia or blackout.

CO2 tables

Static CO2 tolerance tables are used to guide trainees through a simple breath-holding exercise. The goal of these tables is to decrease the amount of time spent resting between periods of holding one’s breath. This will improve one’s ability to withhold a higher level of carbon dioxide. 

When creating your own CO2 table, it’s important that the breath-holding time does not exceed 50% of your personal best amount of time spent holding your breath. Also, one session should not exceed 8 cycles.

For example, here is a static table for someone with a personal best of 3 minutes:

9 ways to increase your CO2 tolerance

If carbon dioxide tolerance training isn’t for you, you’re probably wondering how to increase CO2 tolerance. These techniques can help you increase CO2 tolerance whether you’re a runner, freediver, or just someone looking to improve their respiratory health.

1. Box breathing

Box breathing is also known as square breathing, 4-4-4-4 breathing, or sama vritti. It’s a breathwork technique that involves inhaling, pausing, exhaling, and pausing again for equal amounts of time. This breathing exercise is one of the easiest to do and offers a variety of benefits, including stress relief. Those looking to improve their tolerance will benefit from this exercise, since it incorporates holding the breath.

Top benefits:

  • Helps control hyperventilation
  • Relieves stress and anxiety
  • Lowers blood pressure
  • Promotes calm and relaxation
  • Improves sleep

How to do it:

  1. Sit or lie down in a comfortable position.
  2. Inhale through your nose for a count of 4.
  3. Hold your breath for a count of 4.
  4. Exhale through your mouth for a count of 4.
  5. Hold your breath for another count of 4.
  6. Repeat this cycle as many times as desired.

Best suited for: Everyone from athletes to those with high-stress jobs.

2. Diaphragmatic breathing

A woman breathing while lying down with her hands on her chest and stomach

Diaphragmatic breathing, also called belly breathing or abdominal breathing, is the easiest and most basic form of breathwork. It's a deep breathing exercise that involves breathing in through the nose as you expand your stomach, and then slowly exhaling through the mouth. This makes use of the abdominal muscles and helps establish proper breathing patterns.

Top benefits:

  • Strengthens the diaphragm
  • Slows breathing rate
  • Lowers blood pressure
  • Reduces oxygen demand
  • Promotes relaxation

How to do it:

  1. Sit or lie down in a comfortable position.
  2. Place one hand on your stomach and the other on your chest.
  3. Inhale through your nose, feeling your stomach rise as the air enters your body.
  4. Exhale through your nose, allowing your stomach to lower as the air leaves. Be sure that your chest remains still.
  5. Repeat this cycle as many times as desired.

Best suited for: All athletes, and anyone who wants to improve their breathing.

3. Numbered breath

Numbered breath is sometimes also known as counting breath. It’s a breathwork exercise that is done by increasing the length of exhales, holds, and inhales by one count with each repetition. This is an exercise that's just as great for mindfulness as it is for breath control. It's also considered another relatively easy exercise that gives the lungs a workout.

Top benefits:

  • Slows breathing rate
  • Promotes relaxation
  • Lowers heart rate
  • Lowers blood pressure
  • Improves core muscle stability

How to do it:

  1. Get into a comfortable position and close your eyes.
  2. Exhale through your mouth until your lungs feel empty.
  3. Inhale while thinking of the number 1.
  4. Hold your breath for a count of 2, then exhale for a count of 2.
  5. Inhale again while thinking of the number 2.
  6. Hold your breath for a count of 3, then exhale for a count of 3.
  7. Continue this exercise up to the number 8.

Best suited for: Anyone who needs to correct their breathing.

4. Nose unblocking exercise

The nose unblocking exercise is a breath-holding technique that is typically done to relieve nasal congestion. Since it involves holding the breath while pinching the nose, it also serves as a great way to build CO2 tolerance. This also means this exercise is ideal for anyone who might need to increase the level of CO2 in their body as a result of hyperventilation or breathing through the mouth.

Top benefits:

  • Clears nasal passages
  • Calms the mind
  • Soothes nasal membrane tissue
  • Reduces inflammation
  • Increases circulation in the sinuses

How to do it:

  1. Take a few minutes to normalize your breathing.
  2. Silently inhale through your nose for a count of 2.
  3. If possible, silently exhale through your nose for a count of 3.
  4. Pinch your nose with your fingers while keeping your mouth closed.
  5. Gently nod your head or sway your body until you feel the urge to breathe.
  6. Keep pinching your nose until you feel a strong need for air.
  7. Slowly inhale and exhale through your nose while continuing to keep your mouth closed. Be sure to relax.
  8. Breathe normally for 1 to 2 minutes before repeating.
  9. Repeat these steps as many times as desired.

Best suited for: Endurance athletes, or anyone with asthma or other nasal issues.

5. Nasal breathing

A woman leaning against a stool while breathing

Opting to breathe through your nose with your mouth closed throughout the day, while asleep, or during training is another great way to build up your tolerance. Breathing through the mouth can cause a reduction in the CO2 levels in the body, so nasal breathing can help to correct this. In general, nasal breathing is also ideal in order to establish a proper breathing rhythm.

Top benefits:

  • Increases lung capacity
  • Slows breathing rate
  • Strengthens the diaphragm
  • Reduces risk of coughing
  • Lowers risk of snoring and sleep apnea

How to do it:

  • Remind yourself to close your mouth and breathe in and out of your nose throughout the day.
  • When training, be mindful of closing your mouth and breathing through your nose throughout the practice.
  • When you’re ready to fall asleep, close your mouth and breathe in and out of your nose.

Best suited for: Endurance athletes or anyone with breathing difficulties.

6. Buteyko Breathing

The Buteyko Method is a breathwork technique that consists of various breath-holding exercises. Buteyko Breathing is typically done in order to improve lung function or address general health concerns. The emphasis placed on the ability to hold the breath also allows for building up a tolerance to CO2.

Top benefits:

  • Improves lung function
  • Preserves the health of stem cells
  • Increases resistance to bacterial infections
  • Promotes relaxation
  • Helps regenerate new brain tissue

How to do it:

  1. Sit up straight in a chair or on the floor.
  2. Try to relax your respiratory muscles.
  3. Spend a few minutes breathing normally.
  4. Follow the steps for either the Control Pause or Maximum Pause exercise.

Control Pause

  1. After your last normal exhale, hold your breath.
  2. Use your thumb and index finger to pinch your nose.
  3. Continue to hold your breath until you feel the urge to breathe, then breathe out through your nose.
  4. Spend 10 or more seconds breathing normally.
  5. Repeat as much as desired.

Maximum Pause

  1. After your last normal exhale, hold your breath.
  2. Use your thumb and index finger to pinch your nose.
  3. Continue to hold your breath until you begin to experience moderate discomfort, then breathe out through your nose.
  4. Spend 10 or more seconds breathing normally.
  5. Repeat as much as desired.


These are examples of beginner’s exercises. However, the Buteyko Method is a breathwork technique that consists of a variety of other exercises that can be learned through workshops and training. If you want to see an example of what another Buteyko Breath exercise might look like, watch this video on guided breathwork for controlled relaxation.

Best suited for: Swimmers and freedivers, or anyone with breathing difficulties.

7. Alternate nostril breathing

Alternate nostril breathing, also known as anulom vilom, is a breathwork technique that involves breath control using the nostrils. It works by breathing in through one nostril and breathing out the other on a repeated cycle. This specific technique behind this exercise is used to improve respiratory function and endurance, while also building up a tolerance to CO2.

Top benefits:

  • Regulates the nervous system
  • Lowers blood pressure
  • Improves breathing
  • Reduces stress and anxiety
  • Promotes relaxation

How to do it:

  1. Sit down in a comfortable position and raise your right hand up towards your face.
  2. Close your right nostril using your right thumb.
  3. Inhale through your left nostril, then pause.
  4. Close your left nostril using your right ring finger and release your thumb.
  5. Exhale through your right nostril, then pause.
  6. Inhale through your right nostril, then pause again.
  7. Close your right nostril with your thumb again and release your ring finger.
  8. Exhale through your left nostril, then pause.
  9. Repeat this cycle as many times as desired.

Best suited for: All athletes, and anyone wanting to relax.

8. Pursed lip breathing

https://www.othership.us/resources/breathwork-training

Pursed lip breathing is a breathwork technique that is used to slow one's breathing. It can be easily done by simply inhaling through the nose and exhaling through pursed lips. It's used primarily to improve lung function, but can contribute to a higher tolerance of CO2 as it corrects breathing issues.

Top benefits:

  • Relieves shortness of breath
  • Slows breathing rate
  • Decreases work needed to breathe
  • Increases lung capacity
  • Increases physical abilities

How to do it:

  1. Get into a comfortable position.
  2. Inhale through your nose.
  3. Purse your lips like you’re about to blow air.
  4. Exhale slowly through your lips for twice the length of your inhale.
  5. Repeat these steps as many times as desired.

Best suited for: Endurance athletes, and anyone with breathing difficulties.

9. Active breath-hold exercise

The active breath-hold exercise is another breathing exercise that can help build up tolerance to CO2. This is done by altering inhales and exhales between the nose and mouth. Practicing this technique allows you to train yourself to prefer breathing through the nose. It also helps you maintain more carbon dioxide.

Top benefits:

  • Increases lung capacity
  • Increases cardio strength
  • Improves recovery time
  • Relieves stress and anxiety
  • Increases mental capacity

How to do it:

  1. Hold your breath for 5 to 15 seconds.
  2. Breathe in and out through your mouth 9 times.
  3. Breathe in through your nose and out through your mouth 7 times.
  4. Breathe in and out through your nose 5 times.
  5. Continue to inhale and exhale through your nose until you’re ready to repeat.
  6. Repeat this cycle as many times as desired.

Best suited for: All athletes.

4 resources to learn more about CO2 tolerance

Want to learn more? These resources can provide you with additional information:

  1. Understanding CO2 Tolerance & How To Train It: A guide for athletes on why and how to build up a carbon dioxide tolerance.
  2. Breath Test Calculator: A guide on how to use Apnea Breathing and Cadence Breathing calculators to test your level of CO2 tolerance. 
  3. CO2 Tolerance: A 2020 article on the importance of building a tolerance to carbon dioxide.
  4. The details of CO2 transport and CO2 tolerance for freedivers: A look at the science behind building up a tolerance for CO2 for freedivers.

Want to start improving your CO2 tolerance with breathwork? See what class styles we have to offer on the Othership app.