tl;dr: also leave your furnace fan in the on/recirculate mode rather than auto. -- Also if you have a central furnace, leave the fan in the on/recirculate mod

tl;dr: also leave your furnace fan in the on/recirculate mode rather than auto. -- Also if you have a central furnace, leave the fan in the on/recirculate mode, rather than 'auto'. The power usage of modern furnace fans is very minimal, and the effect on air quality is significant. Especially if your furnace has a fresh air intake, which most do. You can combine that with periodically cracking windows or running bathroom or stove exhaust fans (could even install a switch to automatically run the bathroom fan on a daily schedule). When things are sealed up, the furnace won't pull in a lot of outside air (but the recirculating still helps a lot), and then when you have an exhaust path (fan or window), it will pull in more. Then it's just a matter of finding out how much to exhaust. A bit each day should be fine, or you can get more precise with a CO2 sensor like [1]. Especially in a closed bedroom overnight, it's amazing the difference you'll see with the furnace fan and/or an exhaust fan running, or a window open. 1: https://www.amazon.com/Hydrofarm-Autopilot-Desktop-Monitor-Logger/dp/B01FYWU2IS https://www.amazon.com/Hydrofarm-Autopilot-Desktop-Monitor-L...