John said:
...If anoxia is imperceptible, and results in sudden
fainting, then entering a pool of dense CO2 in the bottom of a closed
space will result in sudden fainting, and this is what I understand
happens. But nitrogen doesn't pool, so unless almost all the oxygen has
gone (absorbed by rusting metal?), you DO realise that breathing isn't
working and can retire quickly.
Regarding CO2, true up to a point. Actually, it takes quite a few
seconds for your body to deplete the blood's supply of oxygen. While
that's happening, you're very aware of the CO2. But how often do people
use concentrated CO2? CO2-related deaths are almost always from
breathing the air in a closed space until the O2 is depleted, and then
the death is due to anoxia, not CO2. As I said before, small amounts of
CO2 are agonizing (put a plastic bag over your head for a couple of
minutes to verify
. You die miserably in CO2, but only if you are
prevented physically from escaping.
Many, many entities have to use huge quantities of liquid N2, liquid He,
and such. When the gases escape uncontrolled into an enclosed space
quickly enough to displace O2, they are _deadly_, simply because their
effects are imperceptible. You die in these gases because you don't
realize you have no oxygen, and have no compulsion to escape.
Deaths have occurred in N2-flooded rooms with doors open, simply because
the victims didn't know they needed to get out. I haven't heard of that
happening with CO2.
jp
