Making the Euthanasia Chamber
If the animal is largely inactive and small enough (CO2 euthanasia is not recommended for animals over 2 pounds), a one-gallon jar or juice pitcher works well, or a one-gallon plastic jug could be used if the top is partially cut off so it will hinge up and can later be taped closed. A box, open only at the top and about the size of a gallon jug, could also be used. Add familiar litter (for rodents), a special toy, or whatever might comfort your pet. Making a little nest and covering it with a cloth, or wadded or shredded paper, may help calm and comfort your pet as much as possible. Covering also prevents wandering about during the final minute. If the animal were free to walk about it would begin to stagger and act drunk or confused before loss of consciousness. This is not something you want to see--not how your pet would want you to remember them, so limit your pet's ability to move about. It may even be possible to get your pet to fall asleep.
If you are using a jar, cover the top with a piece of plastic with a hole made in it for the hose, and another small hole to allow the air to escape as the CO2 enters. You might want to suck on the hose to remove most of the air in the plastic bag containing the baking soda and container of vinegar before putting the hose into the euthanasia container (if you do a good job of pulling up all loose plastic, this step should not be required).
If you must hold the pet in order to comfort it, you could put your arm in the container along with the end of the hose, and wrap a cloth around both to partially seal the opening. The air in the container must be permitted to escape as the CO2 enters, so make sure the top is not completely sealed.
Initially the hose should extend about 2 inches into the chamber. When all is ready, hold the cup or glass through the plastic bag, and slowly pour out half of the vinegar so that it takes about 1 minute to pour one cup out and into the bag (leaving one cup of vinegar still in the cup or glass). You will hear a fizz as the acid reacts with the baking soda. Gas will begin to fill the bag, then flow through the hose and into the euthanasia chamber. Make sure the hose doesn't fall into the liquid, as the expanding gas would then force the liquid through the hose. Since CO2 is heavier than air, it will fall down into the euthanasia chamber mixing with the air, and so gradually increase the CO2 concentration. In 1 to 2 minutes the animal should be in deep anesthesia and breathing deeply. Touching an eye should produce no response. If you are holding your pet, it will be completely limp. If you are not holding the animal and can't see it, just shake the container a bit and listen. There should be no movement. Do not open the container to check or reach in as this will introduce air and possibly reawaken the animal.
If an animal remains alert and appears in distress, the concentration of CO2 was probably too high too quickly. If you tap on the container and there is no response and the animal appears unconscious but appears to be taking deep breaths, that is known as agonal respiration. It is, if it occurs, a normal part of the dying process. So when unconscious or unresponsive, that would be the time to go to the next step of flooding the chamber with pure CO2.
Once unconscious or unresponsive, push the hose down near the bottom of the container and pour out the remaining vinegar into the bag. When most of the fizzing subsides, you might squeeze the bag, if it seems to contain a lot of gas, to force out the remaining CO2. This final flow will flood the chamber with a high concentration of CO2 stopping respiration in minutes if not seconds. Now cover the chamber and wait 10-30 minutes before checking (longer for amphibians or reptiles).
Rats euthanized by increasing CO2 levels to 33% over 1 minute, then killed using high levels of CO2 while still in their home cage showed no signs of stress either by behavior or by subsequent blood tests for ACTH, glucose, and corticosterone which would be abnormal if the rats had experienced anything distressing. 2 This is strong evidence that CO2 euthanasia is as "good" a death as can be achieved in a home setting.
1. One gallon of white vinegar.
2. One pound box of baking soda.
3. Tablespoon to measure baking soda.
4. One-gallon container: Jar, pitcher, plastic jug, or box with opening only at top (euthanasia chamber).
5. Hose, 1/2 inch inside diameter, about 3 feet long.
6. One gallon size plastic bag--zip-lock works well (carbon dioxide chamber).
7. Twist tie to secure plastic bag to hose.
8. 16-ounce cup (measuring cup) or 16-ounce glass.
9. Rubber band or tape to secure hose to cup or glass on the outside near the top.
10. Plastic or cloth to partially seal the top of the euthanasia chamber around hose, or arm and hose, if using a jar or box.
Next: A Variation in Method
The Reptile Feeder Method
The Euthanasia Machine