Forgive my post if it came off aggressive as that wasnt my intention. When I said 30 seconds, it was a small exaggeration. Even 7 seconds when your gasping for air feels like an eternity.. You yourself should know this given that you have been in a position where you needed oxygen desperately.
"Little research". I would love to see any links tor documents that back up your claim that Co2 is good way to go for reptiles, because every single professional herp I have ever spoken to says thats not as quick and painless as you think.
Not to mention, I simply do not buy the 7 second thing. The remaining oxygen in the snakes body would keep it alive for longer then 7 seconds period. Unless you created a vacuum which was possible of sucking the oxygen out of the snake on a cellular level, 7 seconds simple wont happen.
Suffocating isnt this easy thing where its a set time for the animal to pass. I just personally feel that Co2 is DEFINITELY not the best way to go about this. And I really dont think your fully aware of what is going on in the reptiles body during these "7 seconds".
I feel like you may be playing with a chemical balance in the reptiles body that you fully dont understand. All I know is if I had to choose a split second death of having my brain cavity destroyed or "7 seconds" of gasping for air and feeling the stress on my body as my lungs struggle to compress one last time before I go to sleep.. Its really not even a question.