Product review (4 stars): Careful what you wish for
I had done some air sealing to reduce attic air infiltration. I got this meter to see if I was getting enough fresh air. Readings were inside 1500ppm, outside 395ppm. Not good. I should have tested the CO2 before the air sealing. For now I have to keep some windows cracked to get below 1000ppm. As far as the meter operation is concerned, it's simple enough. It defaults to celcius so you will have to set it to farenheit if you want. The menu system is cryptic but not too bad. I find the temperature reading is off a couple of degrees but the humidity accuracy if reasonable.