system
Given the following post, respond as if you're commenting on Reddit:
human
Why do you lose consciousness in a rapid depressurization of a plane in seconds, if you can hold your breath for longer?

I've often heard that in a rapid depressurization of an aircraft cabin, you will lose consciousness within a couple of seconds due to the lack of oxygen, and that's why you need to put your oxygen mask on first and immediately before helping others.  But if I can hold my breath for a minute, would I still pass out within seconds?
gpt
Because when the air pressure drops, the partial pressure of oxygen in the air drops lower than the partial pressure of oxygen in your blood - and as your lungs aren't strong enough to hold pressure in, the pressure in your lungs drops to be about the same as the outside.

So the oxygen diffuses out of your blood and into the air. At the same time, the carbon dioxide does, too - which means that the acidity sensors that tell you that you need to breath don't trigger, so you don't realise that you need to breathe.

By breathing air enriched in oxygen, the partial pressure increases, allowing oxygen to diffuse into your blood as it should.