CO2 tolerance is how comfortable the body is with rising carbon dioxide, which shapes the urge to breathe.
A short hold or a slower cadence lets that urge show up. In 📝Breathwork meeting it without panic is the training, not lasting longer than last week as a score. The phrase is experiential, not a lab blood-gas test, not a diagnosis, and not a freediving claim. Forcing a hold to "improve CO2" is the wrong dose.
Clients feel the urge as heat, a swallow, or a need to gasp. If it becomes panic, tingling, or dizziness, the hold ends and the nose takes a slow cycle. Chest pain is a referral.