+1 here. I worked at an IoT startup with a lot of gas sensors. When we tested the CO2 sensor, we immediately noticed a correlation between early-afternoon sleepiness and high CO2 levels. Opening the door to the outside world lowered levels and within 5 minutes we felt more awake. It changed how I work: I still like to be warm and cozy, but now I'll bundle up and endure changing the air rather than seal every door and window as I used to.
I feel like most of these experiments don't control for air temperature. I feel like cold air has a much more rejuvenating effect than just lowering CO2 levels. Not that they don't matter, but it's not like you'll instantly feel better.
