Death by CO2 will be painful because you'll experience suffocation, which will likely make you abort. Maybe if you're really drunk and you tie your hands together behind your back and seal the doors...
I'd rather not have to suffocate I guess, I just wanted to know if people had used that as a method to suicide. But I'm guessing only the really desperate people who don't have access to other methods have used it before.
Forensic report of a Japanese man who used dry ice in a car. Interestingly, he seems to have selected it over a chacoal grill, for whatever reason. This method does require a large amount of dry ice, but it seems to check out.
I wondered if it was possible to sleep through the worst of the hypercapnia under sedation, but probably not.