> In my own case the big challenge is winter. But usually just a small crack is enough to lower co2 a fair bit during the cold season. Yep - I open a window in

> In my own case the big challenge is winter. But usually just a small crack is enough to lower co2 a fair bit during the cold season. Yep - I open a window in another room of my apartment, and the brownian motion air exchange (as both rooms have no doors) is enough to keep CO2 at around 600 ppm through the night. Without it, it'd probably shoot to over 2000 ppm over the night.