That’s what I learned in my free diving training. If you lower co2 levels and then use oxygen, your co2-triggered urge to breathe will be delayed. Sometimes it

That’s what I learned in my free diving training. If you lower co2 levels and then use oxygen, your co2-triggered urge to breathe will be delayed. Sometimes it’ll be delayed until you’re hypoxic, at which point you could pass out. This happens due to hyperventilation in free diving (and other reasons, though this is the most common). You exhale more co2 than you would while breathing normally, then dive deeper or longer than you should because your blood isn’t the correct chemistry to trigger an urge to breathe when it should.