CO2 tables: what they train and how to do one

Updated October 18, 2026

A CO2 table is a series of breath holds where the hold stays the same and the rest between holds gets shorter every round. Freedivers use it to get used to the urge to breathe — a feeling that comes mostly from carbon dioxide building up in your body, not from running out of oxygen.

Why train CO2 tolerance

Most of the discomfort in a breath hold is carbon dioxide talking. As it rises, the urge to breathe grows, and eventually your diaphragm starts to twitch in contractions. A CO2 table lets you meet that feeling again and again at a hold length you can manage, while the shrinking rests give you less time to clear CO2 between rounds. With practice the same sensations tend to feel more familiar and less alarming, which makes it easier to stay relaxed — and relaxation is what makes holds last.

How a CO2 table is built

Everything starts from your personal best (PB): the longest breath hold you can do calmly, lying down, on dry land. If you don’t know it yet, see measuring your static PB safely.

• Hold: about 50% of your PB, the same every round. Some coaches start closer to 60%; begin lower if you are new to tables.
• Rest: starts at 2:00 and gets 15 seconds shorter each round.
• Rounds: no more than 8.

For a PB of 2:00, the table looks like this:

breathtable never lets a rest drop below 0:30, so there is always time for three recovery breaths and an unhurried final breath. That is why the last two rounds share the same rest.

Running the table

1. Sit or lie down somewhere you can’t fall, with someone nearby.
2. Use the first rest as your breathe-up: slow, relaxed breaths at normal volume, exhaling about twice as long as you inhale.
3. In the last seconds of each rest, breathe out fully, then take a full but unforced final breath — belly first, then chest.
4. Hold. Keep your jaw, shoulders and hands loose.
5. When the hold ends, take three recovery breaths before settling back into relaxed breathing.

The breathing guide explains each of these in detail. In the trainer, the screen, sound and vibration call every step for you, so you can keep your eyes closed instead of watching a clock.

What it should feel like

The first rounds should feel easy. As the rests shorten, the urge to breathe arrives earlier and stronger, and you may feel contractions. That is the point of the table, but it should stay controlled. End a hold early if you feel dizzy, tingly or unusually tired, or if you notice your jaw clamping and shoulders creeping up. Cutting a round short isn’t failing the table — it’s how you keep it safe. In breathtable, “Breathe now” ends the hold and records the real time.

How often, and when to make it harder

Advice varies: some instructors suggest no more than one table a day, others a few sessions a week. What they agree on is that steady, moderate sessions work better than occasional all-out efforts. When a whole table feels comfortable, change one thing at a time — add five seconds to every hold, or start the rests a little shorter — rather than several at once. Re-measure your PB every few weeks and rebuild the table from it.

Common mistakes

• Over-breathing during rests. Fast, deep breathing flushes out CO2 and delays the urge to breathe. It defeats the purpose of the table and makes a blackout without warning more likely.
• Packing extra air. Forcing more air in on the final breath is a deep-diving technique taught by instructors. Dry tables don’t need it.
• Fighting through warning signs just to finish a round.
• Training in or near water. CO2 tables are dry training. Never do them in a bath, a pool or the sea.

Sources

1. SSI — Freediving breath exercises: train smarter, not harder
2. Cape RADD — What are apnea tables?
3. Go Freediving — Training for recreational freediving
4. DeeperBlue — Training for recreational freediving
5. DeeperBlue Forums — A structured approach to CO2 tolerance tables (community discussion, not an official standard)