This discussion is getting as very [OT] as the question: is water a poison?

Back to the topic: CO2 plays an important role in growing plants in a
greenhouse and must be added just like water and menure.
In the greenhouse nextdoor, they grow Gerbera's, CO2 is monitored and kept
on a level of about 300 PPM by burning natural gas. The CO2 meter is an IR
absorbtion meter with a maximum scale of 3000 PPM.
It needs about a month to stabelize the fist time, and must be calibrated at
least every month with standard mixtures of gas. The whole procedure costs a
few thousand guilders a year, not a problem when you grow a few million
guilders worth of Gerbera's.
I think its a pity, but this type of sensors are of no use for amateurs.
You can use simple glass-chemistry to determine the CO2 content. It costs a
lot of time, but gives also a lot of fun!

-----Oorspronkelijk bericht-----
Van: Mike Keitz <mkeitz@JUNO.COM>
Aan: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Datum: donderdag 26 maart 1998 6:17
Onderwerp: Re: [OT] ph and CO2 measurers?


>On Wed, 25 Mar 1998 10:10:56 -0700 Justin Crooks <jcrooks@WYOMING.COM>
>writes:
>>I have seen studies where up to 35% CO2 was mixed with sufficient
>>oxygen,
>>and breathed comfortably for quite some time.  I think the only danger
>>of
>>CO2 is that it typically is the byproduct of an oxygen-consuming
>>reaction,
>>and therefore there is insufficient oxygen to sustain consciousness
>>(and/or
>>life).
>
>If you could quote those studies, it would be more believable.  I did a
>little research, and found that information on C02 is rather scarce in
>the industrial hygiene literature, probably because C02 poisoning is not
>a major problem.  According to the Conference of Governmental Industrial
>Hygienists, Inc's 1980 book "Documentation of TLV's" (Threshold Limit
>Values ?), a 7-10% concentration of CO2 will cause unconsciousness within
>a few minutes, and presumably subsequent death.  This is based on a 1931
>German study.  The recommended limit is 0.5% averaged over 8 hours, and
>1.5% for short intervals (15 minutes).  Higher limits (up to 5%) are
>considered acceptable for people meeting certain medical qualifications.
>Perhaps people who are constantly exposed to high concentrations (e.g.
>Biosphere 2 residents) would be able to adapt to a 10% concentration.
>Spacecraft are designed for about 0.6% or less.
>
>I found no mention of higher than normal O2 concentration providing an
>increase in CO2 tolerance.  From the limited physiology that I know, I
>would think that the amount of oxygen (as replacement for nitrogen)
>combined with the C02 would have little effect.  Two independent types of
>perfusion are at work in the lungs.  One perfusion gets oxygen in, and
>depends on the oxygen level in the breathed air being sufficiently high.
>The other gets C02 out, and depends on the C02 level in the breathed air
>being sufficiently low.  Above a certain level, the body is unable to
>compensate for the acidity of the blood caused by dissolved C02.
>
>However, perfusion is driven by partial pressures, so an atmosphere of
>35% CO2 and 65% O2 may be tolerable if the total pressure is about 1/4 of
>normal atmospheric (not likely to happen in the typical basement "farm"
>except maybe in case of a tornado).  This would be roughly the same C02
>and O2 partial pressures found in normal-pressure air with 8% C02.
>
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