"ozonb" wrote in message ...


This fact is well understood by greenhouse operators who burn gas to
increase CO2 levels to at least 1,000 ppm, 260% above current atmospheric
levels.


1000 ppm is what works for most plants. Plants using C4 photosynthesis are a
special case and might not be better off at that level.
http://earth.geology.yale.edu/~mp364...ge-selection=2

Inside populated buildings, CO2 levels of 3,000 ppm (770% above current
levels) have been measured in homes, schools and offices with no ill
effects.

True, and even higher, such as crowded rooms, parties, etc. I'm sure that
10,000 ppm would be easily reached. But some people would start to show
some mild symptoms at 30,000 to 50,000.


Even most Health and Safety people consider 5,000 ppm (1,300% above
current levels) to be safe.

True. ASHRAE suggests engineers use a design limit of 1000 ppm housing.
Most house ventilation is designed for 4 people not to exceed 1000 ppm.



Medical gas given to people with respiratory problems typically contains
50,000 ppm CO2 (13,000% above current levels) and our lung sacs retain
about 65,000 ppm (16,800 % above current levels).


Yes, the average human breath is 5 percent CO2. Thats 50,000 ppm. It can be
higher !!



Not until CO2 levels get to 100,000 ppm (260 times current levels) is
there any concern about human health.


Thats 10 percent. Personally, I would not want to spend much time in any
place like that.
I'd even say 5 percent is not good. I don't want to breath in any air thats
higher than my exhaled breath.
I would say that there is no health concern at levels below 1 percent
(10,000 ppm)



"All plant life will also benefit from increased carbon dioxide, and much
of the extra food produced by the green revolution is the result of the
warmer and more carbon-rich atmosphere.


Almost all plant life, again, the C4 plants might not be better off.



http://co2sceptics.com/news.php?id=2962





Warmest Regards

Bonzo