Geez, I knew that at one time and I had forgotten all about it. Must be that
blue crayon in my brain.

Carbon dioxide (from dry ice) is a simple asphyxiant. If it displaces
the oxygen in the air it will kill you, but it takes quite a bit of
it. You can be exposed to 30,000 ppm for 15 minutes and still be OK.

Carbon monoxide at 1500 ppm may lead to death, and the 15 minute
exposure limit is 35 ppm for an hour. This is because without the
extra oxygen molecule, CO has a 200 to 300 times great affinity for
hemoglobin than oxygen does. So even if there is enough oxygen
present, the CO will kick it off the hemoglobin and you will die. So
it isn't just a simple asphyxiant any more.



grandma Rosalie