tl;dr I happen to work for a company that specializes in monitoring and managing indoor air quality in dangerous environments/for large enterprises and I happened to stumble across this thread. While the company (Airguard.ai) doesn’t focus on consumers/home applications – working in the IEQ field has sensitized me to the whole issue of indoor air quality.

A few quick thoughts – first in defense of Simone – CO2 levels while you sleep do have a large impact on sleep quality. I would assume this to be largely non-controversial because most people have experienced a bad nights sleep in a stuffy hotel room for instance, but I did see some dismissive comments.

What was surprising for me anyway was that the impact on sleep quality (particularly for women and children) happens at relatively low levels. It would not be surprising to learn that CO2 levels of 3000 have a big impact on sleep, but at 1000?

In fact, increasingly people are starting to think that the negative impacts of CO2 happen at much lower levels than previously thought (starting at around 600). Time will tell, but what complicates the research is that every person is different – so some people seem unaffected by numbers as high as 1500 while others feel terrible.

In any event a recent sleep study (that you can find on pubmed) focused on three levels of CO2 exposure 800, 1900 and 3000. You can find the study here – [Experimental study on sleep quality affected by carbon dioxide concentration] - https://pubmed.ncbi.nlm.nih.gov/32979003/

The conclusions of the study (in my opinion anyway) were not surprising in that the researchers found that “Both subjective and physiological results showed that sleep quality decreased significantly with the increase of CO2 concentration.”

Now the reason why I offer this study is because I think it’s important to firstly be scientific (is there evidence that CO2 exposure when sleeping is likely to matter), but once that has been established then switch to being pragmatic.

This is an N=1 kind of thing – all you need to know is how you feel and at what levels of CO2.

You tell me that you sleep great at 1200 – then sleep at 1200 if it’s a pain to lower it to 600. You tell me you sleep terribly at 800 then try to get it down to 525 or whatever the ambient level is in your area. The science can be a guide – but this is something largely personal – akin to what is the optimal temperature for sleeping (answer being whatever temperature you sleep optimally at – where you are free to define optimally as you like – I personally use time in deep sleep)

That being said – based on what you find out about yourself and your environment this will drive your approach to improving your sleep (notice the mission shouldn’t be to narrowly eliminate CO2, but holistically improve sleep – so don’t forget things like humidity, temperature, noise, light).

Anyhow – If the level of CO2 in your bedroom is 1200 when you sleep – chances are just cracking a window will do the trick (“natural ventilation”). If it’s 2000 - 3000 then perhaps you need some kind of exhaust fan that is sized appropriately to your problem (“mechanical ventilation”). Over 3K and you probably should call in an engineer/HVAC guy and figure out what’s going on in your house – because 3K means that you can safely assume that your whole house likely has poor ventilation – which is not good.

This is a long way of saying – measure first.

I assume you’ve already done this – but if not get an air quality sensor.

So in sum – I would suggest a stepwise approach:
Step 1: Try Natural Ventilation
Step 2: Try Simple Mechanical Ventilation (fans or turn on the bathroom extractor fan)

If these fail then I would have an engineer come in and look at the air flow/HVAC or whatever you have.

Finally you mentioned CO2 capture – As a final option (if you have money to burn) perhaps consider DAC (Direct Air Capture) solutions but it might be cheaper to just move out of the place to be frank.

While it is possible to capture CO2 in your bedroom – it’s almost certainly not going to be quiet (unless you use plants) and while from a scientific standpoint removing CO2 from the air is basically a solved problem (in space craft they use Lithium Dioxide canisters – here is a link to one used in an Apollo mission https://airandspace.si.edu/collection-objects/lithium-hydrox... ) current DAC approaches are almost guaranteed to be either labor intensive, expensive or noisy or most likely all three.

In terms of plants – I saw a somewhat dismissive comment about plants – all I would say here is that plants vary tremendously in their abilities to capture CO2 (and they have the added benefit of cleaning the air) but plant walls DO work. But . . . again it depends on how big your problem is and how much space you have for something like that -- and it will be labor intensive. YMMV.

If you want to know more about the power of plants here’s a link to an interesting article –https://phys.org/news/2013-07-air-hidden-indoor.html

You can find more information about green walls etc here -– https://airguard.ai/insights.

Good luck with finding a solution! Breathe well.