> human body doesn't control for oxygen levels, monitoring instead levels of CO2. So it leads to hypoxia which goes undetected for a some time. I don't think t

> human body doesn't control for oxygen levels, monitoring instead levels of CO2. So it leads to hypoxia which goes undetected for a some time. I don't think that's quite correct. Hypercapnia (excess CO2) triggers a reflex to inhale, that's what you feel when you hold your breath for a long time. That reflex doesn't trigger when you're inhaling CO, for instance. But the body does have sensors to detect oxygen levels in the carotid body (and maybe the aortic body?). These do impact breathing as well, but they do so via the parasympathetic nervous system so you're not as aware of it. IIRC the way this works is poorly understood, and its dysfunction been thought to play a role in sleep apnea.