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Recently I tried holding my breath for as long as I could. I managed to hold it for almost 2 minutes, but after a bit more than 1 minute, I already felt a strong need to exhale some of the air. At the same time, I did not feel like I had to inhale again though. I ended up with two possible explanations:

1. At the beginning, I took a deep breath of air which was about 20 °C in temperature. After this one minute in my lungs, the air warmed up (I assumed it warmed up to 35 °C). For the sake of simplicity, I calculated with the ideal gas law

pV = nRT

that the pressure in the lung would increase by about 5%. Ok, this is why I had to release some air. But wait...

2. From what I learned about physiology, I know that our body has certain chemoreceptors to determine the oxygen saturation in our blood. And there are such chemoreceptors for carbon dioxide as well. The concentration of CO2 in my blood reached a certain threshold and I experienced this strong need to exhale.

Can anybody of you confirm one of these theories? Or are both of them wrong?

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    Try your experiment again but only take half a breath. – Graham Chiu Feb 20 '18 at 14:14
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    Just a quick info: There is no chemoreceptor oxygen saturation, it’s all done via the CO2. This is why carbon monoxide (CO) poisoning is so lethal: It bonds stronger to the erythrocytes than oxygen, but you won’t notice running out of oxygen because the CO2 saturation in your blood doesn’t increase. – Narusan Feb 28 '18 at 21:54

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