Coby Beck wrote:
[snip]
and 200ppm CO2. Too bad humans can't survive at 6000ppm CO2 and probably
not at 1500ppm. Too bad we need things besides primordial ooze to eat.
[snip]

This is interesting. I tried to come up with some figures at too what
the maximum concentration of CO2 was/is but only came up with the
following references using Google:

Lecture, space-craft environment:
"Physiological Limits: keep below 1% = 10,000 ppm; Earth: 350 ppm
Typical levels depending on crew activity: 2,000 - 7,000 ppm (0.2 -
0.7%)"
(pdf)http://www.colorado.edu/ASEN/asen551...vironment2.pdf


NASA-research:
"Environmental Control
20-32 ± 0.2ºC air temperature, 75 - 100 ± 3 % RH,
300 - 3000 ± 30 ppm CO2 , ≈ 21% O2 (≈ 30% O2 if EVA),
catalytic ethylene removal, humidity condensate recycling"
(rtf)http://www.google.nl/url?sa=t&ct=res...KsXWwgGh8dCTBA


Now I realize this still isn't the 24/7/365 exposure you're referring
to, so I'm quite interested what the maximum exposure a human could
endure would be? (I've also got some personal interest here since I'm
living next to one of the most congested/polluted streets here in the
Netherlands.)