Not Me wrote:
snip
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

R,
Tom Q.