How come people in submarines don't run out of oxygen?

Question

How come people in submarines don't run out of oxygen?

Answer 1

they get oxygen from the water

Answer 2

They do. the old WW2 subs were limited by battery life while cruising submerged, but had to surface every 12 hours or so for a change of air. German U-Boats had a Snorkel that allowed them to run just under the surface with a tube erected to reach the surface and allow air to be drawn down to the diesel engines, which also ventilated the boat. Nuclear subs have effectively unlimited electrical power and can process stale air splitting water into hydrogen and oxygen to top it up. This is not done unless absolutely necessary as the hydrogen has to be discarded and leaves a detectable trail

Answer 3

They are experts at holding there breath.

Answer 4

They make their own air.  Here is a link that explains some of it.

Answer 5

The sub makes its own O2.and scrubs the CO2 out of the expired air.

Answer 6

it takes air from above and locks it the brings it downs, its like a bubble

Answer 7

modern subs produce there own oxygen from sea water, and they have "scrubbers" that remove excessive C02 etc from the air.