Close the lid
Warning...a tightly closed completley airtight C02 chamber is also known as a bomb and it will explode. You really don't want it too air tight. An alternative to dry ice is a full c02 paintball gun canister. The next question that always comes up is...when does the gas that killed the rats dissipate enough to make feeding to your snake safe. The answer is instantly. C02 is carbon DIOXIDE not carbon MONOXIDE. Everytime you and every other person and animal on the planet exhales, you are pumping C02 into the air. There is c02 in every breath you breath. It doesn't hurt you. It's when it's all there is and the lack of oxygen that it makes you go to sleep and never wake up. It's not a dangerous gas.
