CO₂ tolerance.
Fixed hold, decreasing recovery. Trains acceptance of carbon-dioxide buildup — the foundational static-apnea protocol for freedivers.
Every table below recalibrates to this number. Don't know yours? Leave it at 2:30 and adjust later.
The method.
CO₂ tolerance tables condition the body to accept rising carbon-dioxide levels — the trigger behind the urge to breathe. Static-apnea holds remain a fixed duration while recovery intervals shrink, gradually shifting the diver's tolerance threshold without taxing oxygen reserves. Train two to three times a week, never alone, and never in water without a qualified buddy.
About this protocol.
What is a CO₂ tolerance table in freediving?
A CO₂ tolerance table is a structured static-apnea exercise where breath-hold duration stays fixed across eight rounds while recovery intervals progressively shorten. Each round starts with more carbon dioxide and less oxygen than the previous one, training the diver to accept rising CO₂ — the trigger behind the urge to breathe — without panic. It is the foundational protocol for freediving breath-hold conditioning.
How often should I train CO₂ tables?
Two to three sessions per week is the consensus across AIDA, PFI, Molchanovs, and Apnea Total. Allow at least 24 hours between sessions for the central nervous system to consolidate the adaptation. Never train two days in a row when you feel fatigued, dehydrated, or unwell.
What hold time should I use?
Exactly 50% of your static personal best, rounded to the nearest 15 seconds. A 3:00 PB diver runs 1:30 holds; a 4:00 PB diver runs 2:00 holds. The hold stays constant across all three difficulty tiers on this site — Apnea Total's explicit guideline is that holding above 50% PB "pushes your limits too far" and turns the table into an O₂ exercise instead. Difficulty is expressed entirely through the recovery profile (Foundational 2:45 → 1:00 / Standard 2:30 → 0:45 / Advanced 2:15 → 0:30).
How long should I breathe up before round 1?
Two to two-and-a-half minutes of calm, unforced ventilation. The breathe-up engages the mammalian dive reflex without flushing CO₂. Do not hyperventilate — fast or deep breathing strips out CO₂ and removes the urge-to-breathe warning that protects against shallow-water blackout. Quiet tidal breathing only.
When can I graduate from CO₂ tables to O₂ tables?
Once you can comfortably complete a Standard CO₂ table at 50% PB with no panic and clean recovery between rounds — typically after four to six weeks of consistent training. O₂ tables push closer to the hypoxic limit, so wait until your CO₂ tolerance is solid before layering them in.
Is it safe to train CO₂ tables alone?
Static-apnea breath-holds carry a real risk of shallow-water blackout — losing consciousness without warning, especially toward the end of a hold. Dry-land static training (sitting or lying down) on land is the safer practice setting. Never train static apnea in water without a trained safety buddy, and stop immediately on visual stars, tingling, or any neurological symptom.