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

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

I don't think this is quite right.
An excess of nitrogen displacing oxygen leads to loss of consciousness
- often without prior warning, while the cognitive response
deterioration is not detected.
An excess of CO2 however, leads to respiratory distress, possibly
panting i.e. we have a physiological , maybe evolved response to the
stuff.

Brian Whatcott