[OutOfHere]

I constantly have two window air purifiers running at home. They lower the indoor CO2 and their filtration also dramatically lowers the indoor particulates. Granted, I can't run them as such in deep winter or deep summer.

Motivated by the article, I will proceed with using a continuous portable CO2 meter when not home.

[woutgaze]

If your air purifier sucks from and dumps into the same room it will do nothing for CO2 levels. Only for dust particulates.

[OutOfHere]

I noted clearly that they're window air purifiers, suggesting that they intake from outside. As such they absolutely bring the indoor CO2 level closer to the outdoor CO2 level. This also happens to be a good way of capturing dust.