Comment by condiment

> Noticeable cognitive impairment starts in the 700-1000ppm range

The US navy failed to detect such effects in submarine crew, even at much higher levels like 10,000 ppm.

Another reason to be skeptical is that exhaled breath is 4% CO2 (40,000 ppm!). Therefore a few thousand extra ppm in the inhaled air should not make much of a difference to the homeostasis mechanisms in our bodies.

>One solution that can help is an external air heat exchanger

I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.

So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.

I have been monitoring for high CO2 for a few months now. I easily find myself in the 1000 - 1400 range for some time before I finally let some air in in winter.

I have not noticed significant cognitive impairment (not saying it did not happen)

My quality of sleep/life have greatly increased since installing an Energy Recovery Vent (ERV) — it exchanges outside/inside air through a membrane, which is about 60-80% efficient for both humidity and temperature re-capture (depending on fan speed).

[•] <https://en.wikipedia.org/wiki/Heat_recovery_ventilation#Ener...>

I use a Panasonic model — readily available from Big Box Retail (~$700 + $100 in vent/conduit) — which can do 20 - 60 cfm (in my 900 sqft home this can easiliy exchange the entire volume several times per day).

> higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition

I am somewhat skeptical of this:

https://www.astralcodexten.com/p/eight-hundred-slightly-pois...

> I think it’s little appreciated that high CO2 levels cause cognitive impairment

Have you been telling representatives? Here's a letter I wrote to mine:

https://pdfhost.io/v/bRJEGptatL_climate-change

This is a meme on hacker news that's usually stated as a fact, but I'm not sure there's any robust evidence of cognitive impairment at <1000ppm

Really? Wow, I try to keep my place at 500-600, without that much effort.

Ok this sounds like BS, what kind of sensor is being used to get such readings? What do you use?

> high CO2 levels cause cognitive impairment

Sounds seriously unlikely. How would this work in practice, at the level of bodily functions?

> perfectly reversible, but that uses a lot of energy

Looks like a perfect match to a solar plant, which provides basically free energy periodically. All you need is a large enough cistern to hold the liquid during night time.

They aren't at risk of halving, though?

https://gml.noaa.gov/ccgg/trends/

Extending the current exponential for 20 years, we get into the 500ppm region.

I don't think that's enough to need scrubbers.

According to https://www.co2meter.com/blogs/news/carbon-dioxide-indoor-le..., at 1000 ppm people start getting drowsy. Let's assume that a decent indoor environment has 300 ppm more CO2 This means that our threshold for when people start getting drowsy even in decent indoor environments is when atmospheric CO2 reaches 700 ppm. For reference, it is currently around 420 ppm, and pre-industrial levels were 280 ppm.

From https://www.climate.gov/news-features/understanding-climate/..., the pessimistic projections suggest that we may reach our 700 ppm threshold by roughly 2070; 45 years from now. (The graphs are hard to read precisely)

The 300 ppm offset compared to the outside air is naturally just an arbitrary number, everything up to 1000 ppm (meaning everything up to 580 ppm more than atmospheric levels) is considered "acceptable". That means any increase in CO2 concentration will take an indoor environment which used to be considered "acceptable" and make it cross the threshold into "unacceptable". An indoor environment which would've been at 900 ppm around the industrial revolution (280 ppm) would've crossed the threshold when we surpassed 380 ppm (which was in 1965 according to https://www.statista.com/statistics/1091926/atmospheric-conc...).

let's compare the past 20 years. In 2004, the concentration was ~377 ppm. That's 47 ppm lower than what was in 2024. An indoor environment which was "borderline but acceptable" at 955 ppm CO2 in 2004 would've crossed the arbitrary 1000 ppm threshold by now, and therefore would benefit from a CO2 scrubber. The next 20 years will likely have a higher increase than the past 20 years, so there will be a larger range of currently acceptable indoor environments which will cross the 1000 ppm threshold by 2045.

TL;DR: It's complicated, 20 years is arbitrary, but as CO2 concentrations increase, indoor quality gets worse so indoor environments which were already bad will become worse. 45 years is a more realistic estimate for when your typical good indoor environment will become unacceptable, but it's a gradient.

https://en.wikipedia.org/wiki/Carbon_dioxide_in_the_atmosphe...

Just extrapolate.

I was also a bit skeptical, but chatgpt gave a pretty good answer I think: https://chatgpt.com/share/69553e26-ea28-8011-bc17-8658fbea4e...

Buildings with higher people/sqft could already take advantage of indoor co2 scrubbers today.

We don't use CO2 to make cement, we use limestone, and CO2 is the byproduct of heating the limestone to make reactive calcium.

You can store CO2 and sell it to construction companies (to cure ferrock), to energy storage companies (who like to put the CO2 in huge bubbles nowadays, go figure), or to agricultural corporations (who enrich greenhouses air in CO2 to accelerate growth).

[dead]