How does a scuba diver’s oxygen tank last for ~1 hour but an astronaut’s lasts ~6-8 hours when both tanks are around the same size?

Question

How does a scuba diver’s oxygen tank last for ~1 hour but an astronaut’s lasts ~6-8 hours when both tanks are around the same size?

In: Technology

Answer 1

All else being equal, astronauts have equipment to scrub CO2 and recover additional oxygen, but divers usually just breathe out and it bubbles into the water through a valve. So astronauts are losing oxygen at a much slower rate. But if a scuba diver had a scrubber, as many military divers do, they could make the air last much longer.