[state_machine]

I did not realize the physiological effects would be as severe:

> The fraction of carbon dioxide is growing: It just crossed 400 parts per million, and high-end estimates extrapolating from current trends suggest it will hit 1,000 ppm by 2100. At that concentration, compared to the air we breathe now, human cognitive ability declines by 21 percent.

[_rpd]

This level of impairment conflicts with data from military studies, for example ...

> CO2 at 40,000 ppm for 2 weeks did not affect performance on multiple tests of cognitive function in physically fit young airmen

https://www.nap.edu/read/11170/chapter/5#54

but it is something certainly worth further investigation.

[antisthenes]

> Twenty-four volunteers, ages 18-23, were selected for their motivation and their excellent health.

If only we were all 18-23 years old in excellent health. The amount of abuse sustained and the speed of recovery my 20 year old self could sustain compared to my 30 year old self is truly astonishing.

When you're young, your body can compensate in a myriad ways you aren't even thinking about, that obviously weren't measured in the study.

It's a good start but not really relevant to the possible scenarios.

1. Dubious sample selection (perfect health, probably above average cognitive ability as well)

2. High levels/short term exposure rather than moderate levels & long term exposure (1+ year)

3. Tests were likely too simple and did not require a high level of abstraction/cognition in the first place.

I know sample n=1, but I've experienced increased anxiety and lower energy levels at ppms as low as 2000-3000, which you can easily encounter in a poorly ventilated room.

[_rpd]

Here's the LBNL study behind the article claims for comparison ...

https://ehp.niehs.nih.gov/1104789/

[e12e]

But seems to be in line with NASA findings:

https://thinkprogress.org/its-taking-less-co2-than-expected-...

Also, the general safety limit for co2 is around 5000 ppm for up to 8 hours - higher than that, and headaches and other effects will manifest.

I'm quite surprised that "no effect" could be seen at 40k ppm - I wonder if there were some limits to the cognitive tests (like the difference between proving a difficult mathematical theorem vs doing some Calculus).

[dmm]

My father certifies hospital gas systems in the US. He's measured CO2 levels in urban areas around 498ppm. Hospital air, the air piped to patients, has a limit of 500ppm. Soon hospitals will have to put CO2 scrubbers on their air supplies just like astronauts.

Maybe head mounted CO2 scrubbers will become fashion accessories for the 1%.

[gorkonsine]

How is CO2 a problem in breathable air? To humans, it's a harmless and inert gas, just like nitrogen. The real problem is too little O2, which humans require for respiration. Obviously, too much CO2 could displace O2 and reduce O2 levels, but it's not the CO2 that's an actual problem (i.e., if the CO2 displaced only N2, and O2 levels stayed the same, you wouldn't have a problem).

So having a CO2 scrubber doesn't seem to make any sense to me, you need something that keeps the O2 levels up. That may be a CO2 scrubber (pulling the carbon atom off the CO2), or it may be more feasible to just carry an oxygen bottle as many elderly people do today. I suspect the latter is the case; if it were feasible to have a portable CO2 scrubber to improve your O2 levels, they would have done it already for all these people.

[Bartweiss]

This relies on several common misconceptions.

Earth's atmosphere is only about 0.03% carbon dioxide. CO2 levels high enough to cause catastrophic global warming still wouldn't displace enough oxygen to matter to humans - it would be a smaller change than a few thousand feet of elevation, which is entirely safe.

The second issue: CO2 is not inert in the human body. It's not used for any crucial reactions, but it's more relevant to us than N2 (largely inert at STP, not while diving) and vastly more reactive than He. That's why divers commonly use Trimix (O2, N2, He), and deep divers use Heliox (O2, He). CO2 is present in solution in your bloodstream at all times, partly as an output of chemical reactions and partly absorbed from the air.

Among other roles, CO2 levels are detected in human lungs - high CO2, not low O2, is what makes you feel the burning "need to breath" sensation. That's why hyperventilating is a common cause of shallow-water blackouts - it lowers blood CO2 levels more than it increases O2 levels, allowing you to run out of air without feeling it.

There's some data suggesting that elevated CO2 levels cause cognitive impairment, which can become quite serious. There's other data (e.g. from nuclear submarines) showing that humans can tolerate CO2 with minimal effect. No one has reconciled this neatly, but it's definitely not true that O2 displacement is the problem.

[gorkonsine]

Very informative, thanks.

[fulafel]

It is harmful in large concentrations as it displaces oxygen (cf. dry ice pool accidents).

[Bartweiss]

True, and dangerous; this even happens naturally when volcanos displace oxygen and create lethal stretches of depressed ground. (https://en.wikipedia.org/wiki/Mazuku)

But not the issue here. CO2 is a tiny fraction of the atmosphere, and apocalyptic global warming happens well before O2 displacement becomes an issue. Bear in mind that humans can function effectively up to several thousand meters - the O2 loss from low pressure is vastly larger than any possible CO2 displacement.

If CO2 is going to have physiological effects via the atmosphere, it's based on chronic exposure and high blood concentrations. There are some studies suggesting that causes cognitive harm, and others suggesting it doesn't.

[yourapostasy]

This is a controversial finding, and not well-accepted nor even abided by where it is a literal life and death matter, like in nuclear submarines [1] or the ISS. Either the LLNL experiment is somehow flawed, or systems designs that crew members depend upon for their lives for months at a time without any pause for the past few decades are poorly designed. By Occam's Razor, I'd rather look at the relatively simpler experiment first before I looked at these complex life support systems, and if anyone is to pursue the LLNL study further, they probably should start there. I'm willing to buy the hypothesis there are cognitive differences, but they would have to adequately explain what has been going on in submarines and the ISS that we missed earlier.

[1] https://wattsupwiththat.com/2012/10/17/claim-co2-makes-you-s...

[kaybe]

Air indoors (and I'm cars!) routinely reaches these levels, easily.