Its not about O2, is about an excess of CO2.

All of these schemes about CO2 capture don't make sense atmospherically (we're physically digging out too much carbon to put it back into the ground economically) -

But CO2 capture makes sense inside buildings.

Of course, all of this is just an extra burden on the individual - buying air filters, CO2 capture, expensive ventilation, CO2 monitors - when we could just restrict our coal and oil usage in the first place, much more economically.