Second reply to critics of my Science Vision report about living o

I believe the main reason to raise the pressure to 1 atmosphere is that
it reduces the evaporation rate of water - at 2.7 PSI water boils at
about 70 degrees C instead of 100 degrees. At low pressure that means
more water loss from your body - you will get more easily dehydrated and
chilled. People at high altitudes experience this on Earth, though there
the problem is exacerbated by hyperventilation due to the lowered oxygen
pressure.

The 'buffer gas' doesn't help much with fire prevention, that's mainly a
function of oxygen partial pressure. Pure oxygen at one full atmosphere
is much more dangerous than pure oxygen at 2.7 PSI, so if you need 1
atmosphere to avoid the water evaporation problem and you want 2.7 PSI
oxygen to avoid fire hazard, you need something else as a buffer.

Note that Apollo, even after the Apollo 1 fire, ran with 5 PSI pure
oxygen once in space. The problem with Apollo 1 was the pure oxygen at
14.7 PSI on the ground.

Arthur Smith