"BF" wrote:

Would you mind explaining the occasion of your CO2 poisoning? I suspect that
you meant CO poisoning, just want to clarify or learn something new.
BF


"ahoy" wrote in message
.. .
The mining people used to say men could work best at 23% oxygen, could
work poorly but still keep going at 15% and at 13% they were taken
out.

23% oxygen is too much. Normally it is 20% or 21% at the most. 19%
is marginal. Oxygen content should be less than 23% but maintained at
levels greater than 18%. 15% is WAY too little. Candles go out at
about 16 percent; 15 percent is the approximate beginning level of
dangerous hypoxia (lack of adequate body oxygen) with increasing,
unrecognized grogginess. At 12 or 13 percent the situation is
critical, and in 7 to 8 percent oxygen death is rapid.

When I was on oxygen after C02 poisoning they had someone in
attendance to remove the mask every so often as the autonomic (?)
brain stem part of your system that makes breathing automatic relies
on the percentages being in proportion. Carbon dioxide level is the
meter that tells you it's time to take another breath it seems.


Carbon dioxide in outdoor air averages about 400 mg/liter or parts per
million. Carbon dioxide toxicity symptoms apparently appear at around
15,000 parts per million or 1.5% and above. OSHA has a Threshold
Limit Value-Time Weighted Average (TLV-TWA), which is the
time-weighted average concentration for a normal 8-hour workday and
40-hour workweek, to which nearly all workers may be repeatedly
exposed, day after day, without adverse effect. The TLV-TWA for
carbon dioxide is 5,000 parts per million (.5% or half a percent.)

Carbon Dioxide (CO2) is the body's regulator of the breathing
function. Any increase above the normal levels will cause accelerated
breathing and heart rate. A concentration of 10% can cause respiratory
paralysis and death within a few minutes.

On Sun, 13 Nov 2005 01:54:33 GMT, Rosalie B.
wrote:

Dave wrote:
On Sat, 12 Nov 2005 22:42:24 GMT, Rosalie B.
said:

Actually an excess of CO2 can be a problem, it's just a problem at a
higher concentration than CO is. The IDLH (immediately dangerous to
life and health) limit for CO2 is 40,000 ppm whereas CO has an IDLH
of 1200 ppm

CO2 is regarded as a simple asphixiant, just like an excess of
nitrogen or any other inert gas.

You're exhibiting the same confusion. The difference between CO2 and CO
is
that CO2 may displace oxygen in the air, reducing the oxygen
concentration
below the level required to sustain life. It is, as you say, an
asphixiant,
but is not a poison. I suspect that the assumption behind the figures
you

The figures I quoted came from NIOSH, and the ppm (parts per million)
are in air. NIOSH's Immediately Dangerous to Life and Health mean
just that -- 40,000 ppm would kill you even though that would be only
.04% if I've got my decimals correct. You could still have enough
oxygen (20%) in air to sustain life even with that amount of carbon
dioxide in the air, but you would have symptoms including headache,
dizziness, restlessness, paresthesia; dyspnea (breathing difficulty);
sweating, malaise (vague feeling of discomfort); increased heart rate,
cardiac output, blood pressure; coma; asphyxia; convulsions; or
frostbite (if it was liquid, or dry ice)

quote is that the remaining gas other than the CO2 is air. Unless I'm
mistaken, you could live for an indefinite period breathing a mixture of
80%
CO2 and 20% O2, just as you could live for an indefinite period
breathing
80% helium and 20% O2. CO2, being inert, doesn't combine with anything
in
your blood's hemoglobin to block oxygen transport.

No you couldn't live for any period of time with that amount of CO2 in
the air like you could with helium which is really an inert gas. It
is a simple asphyxiant but you don't have to have 81% of it in the air
to die from it. It screws up your brain's notice to the body to
breathe. Any gas that displaces oxygen down below about 19% will
asphyxiate you whether it is poisonous or not. For instance Freon or
an excess of nitrogen will both do it.

CO on the other hand, is a true poison in that even if there is enough
oxygen in the air to sustain life, the CO would prevent the blood from
transporting the oxygen from the lungs to the brain and other organs.

Yes you can be poisoned by CO even in the presence of plenty of O2.
Of course it is also true that any burning or other oxidation produces
CO2, but when there's insufficient O2 to form CO2, the CO will be
formed instead. Other poisonous gases are chlorine, and of course
cyanide.

Matter of fact, O2 at high pressure and concentration is poisonous,
leading
to convulsions and ultimately death..

Most of the time what happens with O2 in excess of 23.5% is that there
is so much danger of fire (asphalt becomes combustible in pure
oxygen).

The context I'm familiar with is diving, where part of the decompression
process when you've been breathing helium oxygen mixture involves
switching
to pure O2 at the 60 ft. stop to reduce the partial pressure of the
helium
and flush it out of your system. Can't switch at lower depths because of
the
risk of O2 poisoning at higher pressures.

OK - I was thinking of industrial uses of pure oxygen. Big tanks of
pure oxygen like they have in hospitals or places where they do a lot
of oxyacetylene welding can cause fire problems.

grandma Rosalie



grandma Rosalie