[Stitch4223]

You can get a decent CO2 meter from stores like IKEA. You’ll come to the conclusion that the cozy feeling you get sometimes is directly related to the ppm being well over 1000. It affects your thinking, but it creates “atmosphere”.

The first 440 ppm you’ll get for free. This used to be lower and has risen steeply in the last 100 years and continues to do so.

See the historical graph at https://www.co2levels.org/

[ortusdux]

For homeowners, I highly recommend making sure you have some way to bring it fresh air on demand, and then automate it in conjunction with a CO2 monitor. I added a duct fan and ERV before my HVAC system's fresh air intake, and then tied the fan to an air quality monitor.

[rolph]

people suddenly freaking out, is a cozy atmosphere?

Hypercapnia

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

[Stitch4223]

I wanted to express more like the following:

My personal experience is that when the CO2 levels hit over 1200 in a room, it feels more cozy like a bar or crowded place. With all the up and downsides. Would hate to live in a world where this fog is a constant, as it impedes thinking.