Product review (5 stars): Great product. Performs as advertised
Great product. Performs as advertised.  Additionally, it may change your mind the way you think about CO2 (and climate change) especially when one realizes that to fix the problem with indoor air quality, you circulate more outside air to the inside.  Outside air is considered the baseline for CO2 quality.  But, what happens when the baseline continues to increase?  Worldwide, it averages now 400PPM and is not the the 300-350 that we learned in school.  It is increasing at about 2PPM according to 350.org.  In cities, about 450PPM is to be expected now and in some cases worse.

So, the real issue is you cannot get any lower than the baseline and that is continuing to increase.  At some point, opening the window is not going to solve the indoor air quality problem.