"Coby Beck" wrote in message
news:Hh1Ke.170223$HI.61683@edtnps84...

"Rich" wrote in message
...
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

Yes, figures like those (especially your other post with 5000 as max safe
level for workers) are like what I've seen. Unfortunately, I was just
expressing my own prejudices and not any studies I know of. I don't know
if anyone has looked at constant exposure, and if so surely not for years.
How will a fetus develope for example? What will it do for asthma? Life
expectancy? Immune systems?

It just seems like a Bad Idea to even double what our species evolved to
breathe, let alone x5 (1500) or x20 (6000).

Not that I think this is going to happen. This all sprang out of the
twit-du-jour saying that CO2 levels have been as high as 6000ppm in earth's
history so why are we worrying. We may well be heading for ~1000ppm
though...

--
Coby Beck
(remove #\Space "coby 101 @ bigpond . com")