suffocation in all species of mammal by CO2 poisoning probably feels the same as it does in humans.

Yes, when humans suffocate and die by CO2 poisoning, we fall asleep before we are technically dead.. however, that 30 seconds or longer isn't exactly pleasant. Plenty of people who gas rodents see signs of distress during the process. There may be a method of CO2 delivery that knocks them out before they feel negative effects of suffocating(slowly increasing % of CO2 they breathe I believe is a common technique), but vinegar+baking soda does not provide the kind of precise delivery of specific amounts of CO2 to achieve that.

I am not saying that CO2 is inhumane or wrong, and I have no problems with anyone using it. I just wanted to explain why I believe spinal dislocation is better for the mice. IMO the reason CO2 is popular is just because it makes the person who has to dispatch the feeders feel better about it somehow.

If you use CO2, watch for signs of distress. If there aren't any, then whatever method of CO2 delivery you use is probably just fine. If you see feeders gasping for air and such, you may want to consider a different method of delivery or using spinal dislocation.

If you have issues with rodents dying to feed your pets(or issues with YOU killing the rodents that end up being feeders), maybe you should rethink caring for snakes.