Breathing guides / CO₂ table
CO₂ table
A CO₂ table is breath-hold training for the urge to breathe: eight holds of the same length, with a rest that gets shorter after each one. The holds stay the same, and the rests shrink, so carbon dioxide builds up.
Safety
Safety: Breath holds: lie down, face up. Never in or near water. Never alone.
Breath-hold training can cause dizziness, light-headedness, and, in some instances, loss of consciousness. Don't practice with heart disease, high blood pressure, or arrhythmia.
How a CO₂ table is built
Your hold is a share of your Max Hold, the longest you can comfortably hold today. The rests start at 2 minutes and drop by 15 seconds a round.
| Level | Each hold |
|---|---|
| Beginner | 50% of your Max Hold |
| Intermediate | 65% |
| Advanced | 80% |
An example, for a beginner with a Max Hold of 2:00:
| Round | Hold | Rest after |
|---|---|---|
| 1 | 1:00 | 2:00 |
| 2 | 1:00 | 1:45 |
| 3 | 1:00 | 1:30 |
| 4 | 1:00 | 1:15 |
| 5 | 1:00 | 1:00 |
| 6 | 1:00 | 0:45 |
| 7 | 1:00 | 0:30 |
| 8 | 1:00 | 0:15 |
Your numbers will differ: the hold comes from your own Max Hold, and it grows as your Max Hold does. The rests stay the same.
Posture
Lie down, face up, on a bed or a mat. Never seated or standing: if you black out, you're already down. Never in or near water.
How to do a CO₂ table
- Lie down, face up, on a bed or a mat, with someone nearby.
- Measure your Max Hold first, on a different day from your table.
- Breathe normally for 2 minutes.
- Hold for your hold time, relaxed and still.
- When the hold ends, take a few recovery breaths, then breathe normally for the rest of the rest time.
- Repeat for all eight rounds.
Breathe normally in the rests. Fast, deep breathing clears the carbon dioxide and defeats the table. Expect the urge to breathe to come earlier each round. That's the training.
Who it suits
CO₂ tables are for freedivers and anyone training longer, calmer breath holds on dry land. They're not a relaxation practice.
What the research says
CO₂ and O₂ tables come from freediving practice, not from trials. A 2024 study with 28 beginners compared maximal holds with both tables. The tables didn't push carbon dioxide or oxygen further than maximal holds did, and the authors suggest beginners train mostly with maximal holds (Declercq et al., 2024).
We still think a table is a sound way to practice holding calmly. The honest answer is that nobody has shown it beats simpler training.
Practice it in Pulmonaut
CO₂ Table is in Apnea Lab, for members. It reads your Max Hold, builds the eight rounds at the level you pick, and times every hold and rest with a voice. It won't start until you've recorded a Max Hold.
Questions
How often should I do a CO₂ table?
No study answers this. Leave a day between hard sessions, and stop for the day if a hold feels wrong.
What's the difference between a CO₂ table and an O₂ table?
A CO₂ table keeps the holds the same and shortens the rests. An O₂ table keeps the rests the same and lengthens the holds.
Can I do a CO₂ table in the pool?
No. Never in or near water. Breath holds in water can end in blackout, and blackout in water can kill.
By The Pulmonaut team. Published October 14, 2026. Last checked October 14, 2026.