The prey is not suffocated or strangled by the snake generally. The snake actually compresses the chest of the prey, causing the heart to stop. It's not that they have to get the prey to not breathe for several long minutes, it's generally that the organ compression causes death. I don't have the link to the study, lost that when the laptop crashed.

At any rate, if you cause death either pain-free or extremely quickly, it's humane. So CO2 gas is pain-free, and crushing a skull is quick. People fuss over things like crushing the rat's skull because it's brutal looking, but if it kills the rat, it's still humane. It's the same as a "humane bolt" to the head, after all.

If you're not doing it RIGHT, you can just injure the rodent, or cause slow suffacation or break bones but not kill it... no matter WHAT method you use. And the snake can make a lousy grab and have to take a while to kill the rat too. It's not always going to go RIGHT... no matter what.

So if you do kill your rodents, just make sure you're doing it right.

As far as the bitterants, spray some in your face, esp your mouth. I used to use a compressed air to "fan" my face and get dog hair out of my face at work. Several years ago, the makers put in bitterants and it's REALLY nasty. I certainly don't spray that in my face anymore. It doesn't take turning it upside down to get plenty of that icky stuff coming out too. I don't know how you're using it though, so perhaps the bitterants aren't getting on/to the rats, just the air is. If you think it's humane, that's your decision. I'm not there to see the rats, and it's not my rats.

I think there is a compressed air that doesn't have bitterants, used for the cake decorating and such.