"Not Me" wrote in message
...

"Tom Quackenbush"

| I should also mention that CO is heavier than O2 so the atmosphere
| at the bottom of the rat hole will be have increasingly concentrated CO
| levels. If all else fails the critter will have one h*ll of a head
ache.
|
| C = 12, O = 16, N = 14
|
| CO = 28, O2 = 32, N2 = 28

The real world physics/dynamics is not quite that simple but sufficient to
say CO is heavier than air and will settle to the lowest level i.e. the
bottom of the rat hole.

Brownian motion will cause gases to mix. You don't see the O2 and N2 that
compose most of our "air" separating.