> The window purifiers also keep excess CO2 and VOCs out. I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside

> The window purifiers also keep excess CO2 and VOCs out. I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside the house to leave promptly? (Equalizing it with the outdoors.) Literally "keeping CO2 out" is a much trickier and more-expensive proposition.