[thedoc (OP)]

Max Pizarro asked the Naked Scientists:

Can Humans can survive a 0.13% atmosphere?

What do you think?

[evan_au]

I assume this means 0.13% of normal atmospheric pressure?

Short answer: Unconscious in about 30 seconds, dead in 5 minutes.

Longer answer: Earth's surface has an atmosphere which is about 20% oxygen, 80% nitrogen and 1% miscellaneous (but important). The pressure is about 100 kiloPascals at sea level.

The nitrogen doesn't do very much directly for us, so spacesuits often don't carry it.
You can survive on the 20 kiloPascals of Oxygen, which is about 20% of atmospheric pressure, provided you also have some of the miscellaneous: CO₂ to trigger the breathing reflex, and some water vapour to keep your airways moist.

The oxygen pressure at the top of Mount Everest is about 7 kiloPascals. Some mountain climbers have made the summit without oxygen, but they would die if they stayed up there too long.

So you would slowly die if the air was 100% oxygen, but at 30% of normal pressure.
Lower pressures mean you die faster.

At very low atmospheric pressure, other effects occur like water would boil out of your lungs and skin. Some innovative spacesuit designs are planning to apply mechanical pressure to the skin, without actually applying air pressure. (Your lungs need genuine oxygen pressure!)