The CO2 Tank


Intro: The CO2 Tank

A little about myself and this instructable...

I have owned many snakes as pets and currently have two boa constrictors. And, as all creatures, they need to eat as well. My problem - I don't want to risk my snakes getting injured by killing their prey. We're not talking mice here, either. My two eat things like ducks, chickens, guinea pigs, rabbits, piglets - whatever is a good sized meal.

So I can either throw the animal in there with them alive and watch it scream and die painfully or I can euthanize the animal first to save both animals any pain.

In this instructable, I will explain how I made a carbon dioxide chamber to safely euthanize an animal before I feed it to my snakes.

STEP 1: You Need Some Sort of Chamber

A person making a project such as this will first need a chamber with a tight-fitting lid that is big enough to fit the type of animal that the hungry snake likes to eat.

Remember to consider how big the snake can grow and to choose a container that will accept the proper-sized food for it throughout its life.

I used a metal popcorn barrel. The barrel was painted, and I drilled two small holes into it - one near the top and one near the bottom.

Take care when drilling that the hole is the proper size to accept the tubing that will be used later.

As an optional step, I cut out a hole in the lid and used epoxy to fit a scrap piece of plexiglass so that I can see inside. I have found this very helpful when administering the CO2.

STEP 2: Attatch the Tubing

For this, I used small aquarium tubing. I fed about an inch of tubing through each hole and held them in place with epoxy. Use enough epoxy to create an air-tight seal.

The bottom inlet is for the CO2 and the top is an outlet to allow air to escape.

STEP 3: The CO2 Tank

I used a regular 20oz. CO2 tank made for paintball guns. To it, I attached a valve that controls the amount of gas released and to the valve, I connected a fitting that accepts a tube.

When I went to buy all the parts, I went to a local shop that specializes in paintball accessories and explained to the clerk what I needed and he set me up with the proper parts.

The tube connected to the CO2 tank connects to the bottom tube in the chamber.

Clarification by user french t0ast:
The part that screws onto the valve of the tank is called a "on/off ASA" (Air Source Adapter).

The output from the ASA is threaded at 1/8" NPT.
The black tube coming from the asa is called macro line.

So you would need
co2 tank
on/off asa
Macro line
Macro line fitting (1/8th)"

STEP 4: The Air Trap

When filling the chamber with gas, the air will escape through the top tube.

The last thing you want is for air to be able to get back in after administering the gas. To solve this, the top outlet tube goes into a cup or bowl of water. This allows the air to escape and bubble out, but it cannot come back in.

The reason why: When euthanizing the animal, oxygen leaking back in can prolong the death and also cause it to choke. In my opinion, if the animal is giving its life to feed my snakes, then it deserves to die quickly, painlessly and most of all - with dignity. I have the utmost respect the animal, same as I do for the ones that die to go on my dinner plate.

STEP 5: Administering the Gas

The gas is leaked in when the valve is turned on, slowly filling the chamber from bottom to top. The animal breathes in the gas and dies. If done properly, it will look as if the animal went to sleep and it won't choke or struggle.

Start with a small flow at the beginning. Too much too fast and the animal will panic and/or choke. Once the animal seems groggy and lays down, slowly increase the flow. At this point, the animal will appear to faint. Continue with the gas until the chamber is completely full with gas. Since CO2 is clear, you will have to judge when it is full. Wait two minutes or so and add more gas. At that point, the animal is dead, but sometimes it is hard to tell. Just let it sit for about five minutes or so. After that, shake the chamber and if the animal is not responsive, then it is dead.

Take care when removing the lid. Fan it slightly with the lid or something to prevent yourself from inhaling any gas. The animal will most likely have soiled itself and a layer of bedding will make for an easier cleanup.

When doing two or more animals at one time, such as a litter of mice, take care to not overcrowd the chamber as this will stress the animals and cause panic. Administer the gas as normal.

The most important part is not to stress the animals. When done properly, the animal dies very calmly and does not choke or panic.

At this point, the dead animal can either be fed to the snake or frozen for later.

STEP 6: Thoughts and Tips

You are a pet owner. You have a duty to keep your pet safe and healthy. Your pet can rely on nobody but you to provide it with what it needs to live.

A snake's temperament is caused by many factors such as the species and also how it is treated. Weaning a snake from eating live prey to accepting pre-killed prey can help it to become comfortable with handling and help to reduce the risk of the handler getting bitten. After all, it will no longer have to kill for sustenance. A snake is also less likely to strike when it is full. Handlers should also take care to wash off any scent of prey from their hands as a snake can easily mistake a scented hand for a meal. Check with the seller and with books to determine how often a snake will need to eat before you buy it.

Food can easily be frozen and stored for later use. It can be left to thaw on the counter and when completely thawed, warm the body with warm water. This can be done by putting the animal in a zip-lock bag and placing it in a container ot warm water for 10 or 15 minutes. Be sure that the animal is completely thawed as you do not want your snake to eat any ice. This can cause it to get sick, become too cold, or regurgitate the meal.

To convince a snake to begin taking dead prey, you can try rubbing the food on a live prey item to cover it with the scent of food. Forceps can be used to wiggle the food in front of the snake and cause it to strike. I use grill tongs for this as it keeps my hands a safe distance away from the snake when it is eating. After a while, the snake should become used to eating this way and it will become easier. I never have to scent the food anymore - the snakes are used to the food the way it is and they strike and wrap it as usual.

Last, but not least - as a responsible pet owner you are responsible for providing the snake with proper nutrition. The snake derives its nutrition from the food it eats, so the prey must also be healthy. Prior to gassing, feed the animal for a couple of days with quality food. Also, a good time to gas is after it has been observed eating. This ensures that there are extra vitamins and protein inside the animal's stomach that the snake will benefit from.

In closing, snakes don't eat tofu. An animal has to die for the other to live. But, with care and compassion, an owner can ensure a quick and painless death for the prey and prevent injury and vet bills when the live prey fights back. Most all types of snakes will accept pre-killed prey and it is easy and economical for the owner. Rats and mice come already frozen, but to a person with larger snakes (like me) or with a large collection who breeds their own food, this is an easy and economical way to euthanize prey.

STEP 7: Additional Info

To read more on the subject of humane euthanasia of feeder animals, you can read what the American Veterinary Medical Association has published:
AVMA & humane euthanasia

or from the University of Iowa:
University of Iowa Animal Research

Guidelines for the Euthanasia of Rodent Feti and Neonates
Yale University's IACUC co2 euthanasia guidelines
University of California's euthanasia guidelines

Please note that these guidelines apply mostly to laboratory animals, as some mention the use of barbituates and other gases. But, the CO2 method is widely practiced and acceptable as a rather humane way to euthanize small animals.


The CO2 method is far from perfect. Hold your breath for as long as you can, or breath in and out of a plastic bag for a while. Feel that pain in your upper chest and your head? That's not oxegen deprivation, it's CO2 intoxication. If you can find a canister of N2 (nitrogen), this will give the same result (i.e. a dead animal) but more humanely. If you're gonna ignore me and stick with the CO2, you're as well off drowning it, save you buying any gas at all. Having said that, I do agree that your way is more humane than most poisons, which can then be transferred to the snake too.
My two cents is use nitrogen. It’s available at welding supply stores, it’s pretty abundant even in our atmosphere that’s way we don’t detect N2 concentration like we notice CO2 changes.
Helium works well. People have died from inhaling it to make high pitched vocal messages over the phone. They don't even know they've used too much until they lose consciousness and by that time there is little chance of reviving them because of the blood saturation effects. They don't go through death through symptoms because helium is natural in Earth's atmosphere so it's quite humane to use.
 Liquid nitrogen is easier and cheaper if you can find it, most colleges and universities will sell it for about $2 a liter and you can carry it in a thermos. You could just put it in a sealed container and run a tube from the container to the gas chamber. Since the suffocation response is entirely controlled by CO2 levels, replacing all the CO2 and O2 in the chamber with N2 will cause the animal to pass out and die just from lack of O2, completely painlessly.
i know this post is years old but im still hoping for a reply, if i use the CO2 method or N2 to kill feeders rats for my ball python, it doesnt hurt my ball python to eat the poisoned rat does it...?
 Yep, that's what I was getting at. Just didn't realise it was so easy to get, thanks! :)
I work professionally for the Fed in Food Inspection at a beer slaughter plant, so I have some experience with humane handling of animals for food. My two cents on this after years of reading is you should consider doing exactly this, but Nitrogen instead of CO2. You can get refillable nitrogen tanks at a welding store. CO2 is good if you go slow and don’t overexcite the animal. But our brains ultimately can tell the difference because CO2 concentration is what they’re trained to sense for, so it could be painful in some cases, no way to tell if that animal doesn’t vocalize. But nitrogen changes remain undetectable by the brain because it’s so abundant in our atmosphere animals aren’t trained naturally to sense that shift, and it’s probably like falling asleep in a dark room forever. So for the same amount of work, and substituting Nitrogen, this is a very humane way to do things before slaughter for food for anyone who owns livestock animals.
Is it wrong that I want to build this even though i don't have a snake?
On a different note, where can I get hydrogen cyanide?
Is CO2 cheaper than helium? You could also use helium which is natural in the atmosphere. You can get a helium tank at a party supply store but you may have to get a fitting to replace the balloon nozel.

Hi, my son just got a 5 year old female ball python 2 days ago as a rescue. She has always eaten live food. Is it too late to try frozen? Thank you in advance for any advice you may have. Hope you have a great day! :)

It's never too late for swapping to f/t. It will be much easier to swap to freshly killed first until you can move to fully frozen ones.

my question is it dangerous to touch the hose when co2 is flowing through it?

I know this post is years old, but i really need help, so if i use this method, and feed the poisoned rat to my snake, it wont hurt my snake, right?
Nope it won't hurt your snake. Also, the rat isn't "poisoned" - it's just been suffocated with carbon dioxide (which we all exhale naturally).

This is a good way to feed your snake without it getting hurt. Good luck.
Interesting...How does this compare in price and ease to buying commercial prekilled food?
Buying commercial prekilled food is easy and convenient if you have 1 or 2 snakes. Especially if the snakes aren't very big.

I had several snakes back when I did this, and the boas were rather large. I started breeding mice and rats and used them to feed my snakes and sold them to other friends of mine to make some money on the side. Also, my boas liked food a little larger than rats, so I would buy rabbits, guinea pigs and other food for really cheap at an animal auction. They were live, so this is the way I would euthanize them.

I'm married now, so I had to give up my snake hobby.
Cute snake! Personally im a lizard guy but i still love snakes(and all reptiles).
one time found a 5 lined skink back behind my house. i kept him for about 3 weeks, but he refused to eat so i let him go
My friend has a ball python and the things are freaking awesome. The night i slept over they feed the snake and it was cool but i kind of felt bad for it. Are there any other less expensive ways to do this
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