eli5: How do small spaces run out of oxygen and why can it be deadly?


This whole missing submarine has got me confused regarding the limited oxygen. How is it limited and what makes it deadly? How does the oxygen “run out?”

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Oxygen is consumed by life, and it’s effectively a sealed container with a limited amount onboard.

If you have no source of fresh oxygen, you’re doomed.

Why? Because when you breathe in oxygen, you exchale carbon dioxide, which is something we cannot breathe. Carbon dioxide will fill the space, and since there’s no more oxygen, eventually you’ll die.

Anything below 70% oxygen saturation is life threatening

When you breathe you consume the oxygen. You breath out carbon dioxide. In an enclosed space, there is only a limited amout of oxygen, and when this amount is converted into carbon dioxide by breathing, you suffocate

The oxygen is limited because it’s a enclosed submarine surrounded by water. It doesn’t have the ability to generate oxygen itself so it only has what it’s brought down with it.

The oxygen is running out because the humans are breathing it and converting it to Carbon Dioxide. It’s not like the oxygen is being destroyed or ‘lost’, it’s being bound up in a new molecule. When they refer to “oxygen” in this case, they are referring to what’s called “molecular oxygen” or the molecule O2. Once enough of the O2 has been breathed in and converted to CO2, the crew will lose consciousness and eventually die.

Humans and living animals are turning oxygen into carbon dioxide (CO2) all the time. CO2 is effectively a poison in high doses and must be gotten rid of in enclosed spaces. It would be replaced with oxygen from some storage tank.

Lack of oxygen will cause humans to initially behave strange, sometimes like they’re drunk… but eventually pass out, enter a coma, and cause brain damage. The brain needs oxygen or it will die surprisingly fast compared to the rest of the body.

This is why giving someone who’s heart isn’t beating CPR as soon as possible is so important, but in the CPR situation the air around us is clean. Inside a sealed up submarine, the air you bring with you is all you really have and it will eventually run out as long as living humans are onboard, and CPR won’t help here.