I live in a large apartment (3 adults, 2 children to 1700 square feet). Recently I bought a good CO2 meter (Aranet4) and I really discovered how much you have to ventilate to keep CO2 levels under 1000ppm.

I sort of knew this for a long time and that's why I, for example, always sleep by an open window. But knowing it is one and actually seeing a completely different thing.

So this caused me to start thinking about installing one or more of these boxes in my apartment.