# CO2 sensors in animals? **URL:** \ **Category:** Factual Questions\ **Created:** [October 25, 2018, 1:39am UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472 "2018-10-25T01:39:31Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [October 25, 2018, 1:39am UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/1 "2018-10-25T01:39:31Z")
I’m curious if animals besides humans detect carbon dioxide buildup in the bloodstream, the way humans do. (As I understand, we don’t sense the absence of oxygen … just a buildup of CO 2.) Is this trait common to all primates? All mammals? I ran across the AVMA guidelines for humane euthanasia and for rodents, guinea pigs, etc. and they call for carbon dioxide chambers. Does that not cause the same panic & other reactions in non-humans? (Still looking for a non PDF link for y’all to cite.) ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 25, 2018, 2:40am UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/2 "2018-10-25T02:40:50Z")
Are you sure it isn’t Carbon Monoxide? Because that is real sneaky – people don’t realize that they are suffocating from it. (My uncle did car repair in his garage, and one time the exhaust hose to the exterior came loose, so the car exhaust was going into the garage. He passed out without any awareness, and would have died if someone had not come by in time. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [October 25, 2018, 2:47am UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/3 "2018-10-25T02:47:46Z")
Page 24 of the document shows that it does cause distress. > [@](#): > > Carbon dioxide has the potential to cause distress > in animals via three different mechanisms: (1) pain due > to formation of carbonic acid on respiratory and ocular > membranes, (2) production of so-called air hunger and > a feeling of breathlessness, and (3) direct stimulation of > ion channels within the amygdala associated with the > fear response. > **[AVMA guidelines for the euthanasia of animals](https://www.avma.org/resources-tools/avma-policies/avma-guidelines-euthanasia-animals)** > > The AVMA guidelines for the euthanasia of animals provide veterinarians guidance in relieving pain and suffering of animals that are to be euthanized. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 25, 2018, 2:50am UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/4 "2018-10-25T02:50:25Z")
> [@Tim\_T-Bonham.net](#): > > Are you sure it isn’t Carbon Monoxide? He’s talking about carbon dioxide. ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [October 25, 2018, 12:14pm UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/5 "2018-10-25T12:14:19Z")
Well, there’s one advantage of using carbon dioxide to murder your lab animals - if there’s a leak in the gas chamber, your human lab staff will be able to sense it, for the same reasons you outline above. But yes, I don’t see how this is legal. There are federal guidelines for research on vertebrates, and you’re not supposed to call unnecessary pain. (unless the science requires it, of course!) ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [October 25, 2018, 12:20pm UTC](https://boards.straightdope.com/t/co2-sensors-in-animals/823472/6 "2018-10-25T12:20:47Z")
To go into more detail, many rodent breeders will set up a little CO2 chamber using a canister of gas and a regulator. The process is usually described as turning the regulator juuuuust a smidge, to let in a bit of carbon dioxide, and when the animals are lethargic or actually asleep, to crank it up to lethal doses. So my curiosity is about that intermediate step, where the CO2 levels are high enough to cause sleepiness (instead of panic, scrabbling at the walls, squeaking, or other signs of distress). Is it a matter of size, where humans are big enough to withstand the effects long enough for our brain sensors to go, “Hey, waitaminnit, ohshit!!”