Unfortunately that doesn't seem to work for me. Right now my room has > 1200ppm CO2 (due to closed doors/windows) but I don't feel sleepy at all It's

Unfortunately that doesn't seem to work for me. Right now my room has > 1200ppm CO2 (due to closed doors/windows) but I don't feel sleepy at all It's a very gradual difference. If you're doing something interesting at 1000-2000ppm you probably won't feel sleepy, but it will probably be harder to focus on something you don't find stimulating and you'll be more inclined to feel sleepy.