[kazinator]

> As it entered the tube, the Berkeley air contained CO2 in concentrations ranging from 410 ppm to 517 ppm. When it came out the other side, the scientists could not detect any carbon dioxide at all, Zhou said.

This sounds like it could be the basis for a respirator-like breathing apparatus, not requiring tanks, for entering and staying in enclosed spaces where the concentration of CO2 is high. (Provided there is enough oxygen.)

[hansvm]

That feels super dangerous. CO2 is mostly fine to breathe, but it triggers the impulse to breathe. Without it you won't feel that you're running out of oxygen.

[surfpel]

That's CO2 IN the blood that "triggers breathing". Unless you plan to inject the powder, that's not really an issue.

[hansvm]

What I mean is that scrubbing the CO2 leaves you in a scenario where the air is just as dangerous as before (no oxygen) but you don't have any reflexes or senses letting you know of the danger.

[K0balt]

It’s the co2 in your blood that you make in your body( not that you breathe in) that makes you want to breathe. You can breathe pure oxygen and you will still feel the need to breathe, because your body uses the oxygen to make co2 which then needs to be expelled.

[hansvm]

That only applies (gives you a trigger that you should breathe when the environment is dangerous) if you never exhale though. Is that really an argument for the technique being safe?

[kazinator]

What if that's not the case though. Spaces that are high in CO2 are dangerous because the CO2 has displaced the oxygen below a safe percentage. Maybe by scrubbing the CO2 we can increase the oxygen concentration.

[telgareith]

That assumes you're breathing something besides pure oxygen.

And the "device" is called a 'rebreather.' https://en.m.wikipedia.org/wiki/Rebreather

[Zenzero]

Any context in which it is being used as a scrubber would be one where the people designing it would 100% be aware of this.

[jjk166]

You produce the CO2 that causes the impulse to breathe. That's what you are exhaling.

[hansvm]

Right, and you want that. Scrubbing the CO2 without adding oxygen leaves you in a state where the air is useless and your body can't tell.

[jjk166]

Scrubbing the CO2 from the air has no effect on it. The CO2 that tells you to breathe is not in the air. You exhale the CO2 because you specifically do not want it, you need to get rid of it. Hence the scrubbing.

If there is not enough oxygen in the air to breathe, having more CO2 in the air will not save you.

[kazinator]

If we mix, say, 25% CO2 and 75% regular air, we will get something which still has oxygen, but at too low a concentration to support breathing: the oxygen will have dropped from 21% to around 16%. That's still a lot of oxygen, but not at a breathable concentration. If all the CO2 is removed, then the breathable air is recovered.

[telgareith]

Simple rebreathers use pure oxygen, and even when they don't- as long as co2 is steadily scrubbed out, its little more than a regular scuba regulator.

Oxygen has to go above a certain partial pressure (happens at a couple meters down, I don't know the numbers of the top of my head) before it's toxic. And, carrying a tank that's got more than oxygen in it defeats the original military development and use model of rebreathers: no bubbles, and long submersion times.

The real problem for users is a lot of carbon dioxide scrubbing compounds will kill you if they get wet.

Engineering wise, I seem to recall pressure balancing (countering the water's pressure), and forcing your exhalation air through the scrubber being the complexity.

Theres a ton of complexity with rebreathers. And, thats before accounting for the fact they're mostly used in combat and cave diving. (Last I checked. Tbf, I got scared and changed career paths away from the sea after Rouge Waves became irrefutable fact)

[K0balt]

You don’t need co2 in the air to tell you to breathe. Your body makes co2, which is what you feel. Once you run out of oxygen to make co2, you are already unconscious.

If you go into an area with no oxygen, you will pass out very quickly with little warning except being dizzy, but you will not fail to feel like you need to breathe.

It might be slightly more safe to enter into a room full of co2 than a room full of nitrogen, because you might be alerted by the high co2 a few seconds before the dizziness takes over, but that doesn’t make rebreathers dangerous because you will forget to breathe. If you run out of oxygen, you’re unconscious in a few seconds anyway, co2 or no co2.

[eszed]

With real-time detection (I'd expect that exists, but don't know for sure) you can divert some of the airstream through this scrubber to target a particular concentration of CO2.

[telgareith]

You don't need any CO2. Oxygen bottle, co2 scrubber, pure oxygen purge prior to diving... and you've got yourself a rebreather.

https://en.m.wikipedia.org/wiki/Rebreather