Extremely bad idea!!! Yes of course it works! So does putting them in the freezer live (like someone else in another DIY thread), so does grabbing them by the tail and smashing their heads!!! But if you do any of the above you are guilty of animal cruelty. CO2 should only be used with a regulator since 100% CO2 will burn the rodents respiratory system and make them suffer a horrible death. Please be kind and respectful to those animals that are going to be used for food.