hypercapnia

That means that CO2 levels would have to increase 25 times their current level in order for your fear of hypercapnia to become a problem.

All of them involve intentionally and temporarily invoking hypercapnia (high CO2) and hypoxemia through slower breathing and/or breath holds.

Direct effects on brain physiology: When CO2 levels rise in the blood (hypercapnia), it causes vasodilation of cerebral blood vessels.

The problem in such cases is mild hypercapnia and increased work of breathing (Respiratory loading).

However, the respiratory loading and hypercapnia are extremely mild in the case of clogged respirators.

Of particular note: hypoxia is painless, only hypercapnia (too much CO2 in the blood) hurts.

You can over-optimize for any of those at the expense of the other (see: hypercapnia).

Elevated CO2 levels (hypercapnia) can also seriously reduce your cognitive capacity via multiple mechanisms.

If you exert yourself and don't ventilate effectively then hypercapnia can hit you hard.

Even in your link to the Permian–Triassic extinction event, one of the most probable causes of loss of marine life was hypercapnia.

Diver's Alert Network states that full face snorkeling masks can cause dangerous hypercapnia unless they have tight seals and working one-way valves.

The urge to breathe is driven primarily by increasing blood CO2 levels (hypercapnia).

Not to mention the hypercapnia induced tetany is very uncomfortable and seems a clear signal from the body that "this isn't good!".

That was dangerous due to the risk of hypercapnia: "increased CO2 levels could lead to unconsciousness which, if happening while in the water, can result in drowning.".

Hypercapnia (excess CO2) triggers a reflex to inhale, that's what you feel when you hold your breath for a long time.

Hypercapnia in general can cause short term cognitive issues but not long lasting issues.