Quote Originally Posted by RoyalGuardian View Post
.. replacing anything in the lungs is suffocation no matter how fast or slow you do it my friend. Then again CO2 is sometimes used by people to get high in the fact that if you inhale it you basically black out ( NEVER EVER EVER DO THAT!!!!! I had a friend do it once* then again he was an idiot and he was driving* and he crashed his car into an apartment.) Your "drowsiness" is more like passing out. Those of you who have experimented with duster know what it feels like.
Royal Guardian, CO2 is perfectly humane.

If you read on the subject: At high concentrations (70-100% concentration) CO2 will increase the pain threshold, and will have a anesthetic effect in 12-50 seconds for rats, depending on concentration used. (AVMA , p. 11)

WELL before the animal feels any sensation of suffocating. They are quickly knocked out and are not aware of the lack of oxygen. They have no sensation of hypoxia.