Breath Hold CO2 Table Timer

READY
02:00
Step 1 / 14

Running order

  1. 1.Breathe — 2:00 02:00
  2. 2.Hold — 1:00 01:00
  3. 3.Breathe — 1:45 01:45
  4. 4.Hold — 1:00 01:00
  5. 5.Breathe — 1:30 01:30
  6. 6.Hold — 1:00 01:00
  7. 7.Breathe — 1:15 01:15
  8. 8.Hold — 1:00 01:00
  9. 9.Breathe — 1:00 01:00
  10. 10.Hold — 1:00 01:00
  11. 11.Breathe — 0:45 00:45
  12. 12.Hold — 1:00 01:00
  13. 13.Breathe — 0:30 00:30
  14. 14.Hold — 1:00 01:00

Total 15:45 across 14 steps.

A CO2 table trains tolerance to rising carbon dioxide by holding the breath for a constant duration while progressively shortening the recovery breathing between holds. The hold stays the same; the rest shrinks. That is what distinguishes it from an O2 table, where the rest stays constant and the holds get longer.

A typical table runs seven or eight holds of a fixed length, with recovery starting around two minutes and dropping in fifteen-second steps. The whole session takes fifteen to twenty minutes. The hold length is set at a comfortable fraction of your maximum — this is a tolerance session, not a maximum-effort one.

Never in or near water. Ever.

Breath-hold training in water can cause shallow water blackout — loss of consciousness without warning, which in water means drowning. It kills experienced, fit freedivers every year, and it does not announce itself: the urge to breathe is driven by carbon dioxide, and training to suppress that urge removes the warning that precedes losing consciousness.

Dry training on land, sitting or lying down, is the only form of this that belongs on a page like this. Never practise breath holds in a pool, a bath, or open water without a trained buddy following recognised freediving safety protocols — and even then, never on your own judgement alone.

CO2 tables versus O2 tables

A CO2 table keeps the hold constant and shortens the rest, which raises accumulated carbon dioxide and trains tolerance to the urge to breathe. An O2 table keeps the rest constant and lengthens the hold, which trains tolerance to low oxygen.

They are different stresses with different risk profiles, and CO2 tables are usually considered the more appropriate starting point for dry training. Mixing them arbitrarily within one session is not a protocol, it is confusion.

Setting the hold length

Take a comfortable maximum hold when fresh, then use roughly forty to fifty percent of that for the table. If your relaxed maximum is two minutes, holds of fifty to sixty seconds are a sensible table.

The final holds should be genuinely uncomfortable and completable. If you are failing holds in the second half, the hold length was too long — shorten it rather than pushing through, because pushing through is how the practice becomes unsafe even on land.

A representative CO2 table. The hold is constant; the recovery breathing shortens each round. Set the hold at roughly 40–50% of your relaxed maximum.

CO2 table structure
Round Breathe Hold Note
1 2:00 1:00 Should feel easy
2 1:45 1:00 —
3 1:30 1:00 —
4 1:15 1:00 Discomfort begins
5 1:00 1:00 —
6 0:45 1:00 Notably hard
7 0:30 1:00 Final round
  • Dry land only, sitting or lying down. Breath-hold training in water risks shallow water blackout, which kills experienced freedivers every year.
  • Failing holds in the second half means the hold was too long. Shorten it rather than pushing through.

Source: CO2 and O2 table structures are established freediving training conventions, widely documented in freediving instruction material

Sources

  1. CO2 and O2 table structures are established freediving training conventions, widely documented in freediving instruction material , TheTimerLab — accessed 2026-07-28

🔗 Related Timers

Wim Hof Retention Timer

Wim Hof Breathing Timer

Box Breathing Timer

Breathing Timer

4-7-8 Breathing Timer

❓ Frequently Asked Questions

What is a CO2 table?
A breath-hold session where the hold length stays constant and the recovery breathing between holds shortens each round. It trains tolerance to rising carbon dioxide and the urge to breathe that comes with it.
Can I do this in water?
No. Breath-hold training in water risks shallow water blackout — loss of consciousness without warning, which in water means drowning. It kills experienced freedivers every year. Dry land only.
Why is shallow water blackout so dangerous?
Because it gives no warning. The urge to breathe is driven by carbon dioxide, so training to suppress that urge removes the very signal that would otherwise precede losing consciousness.
How is a CO2 table different from an O2 table?
A CO2 table holds the breath-hold constant and shortens the rest. An O2 table holds the rest constant and lengthens the hold. Different stresses, different risk profiles — CO2 tables are usually the starting point.
How long should the holds be?
Roughly forty to fifty percent of a comfortable maximum taken when fresh. A two-minute relaxed maximum suggests fifty to sixty second holds. This is a tolerance session, not a maximum-effort one.
What if I cannot complete the later holds?
The hold was too long — shorten it next session rather than pushing through. Pushing through is how the practice becomes unsafe even on dry land.
TheTimerLab