Product review (2 stars): CO2 constantly beeping.
I took it out of the box, plugged it in and it started beeping, the CO2 reading was up originally over 1800 and gradually went down, took about a half hour for it to get down to 1455 then started going up and down between 1400 - 1800, constantly beeping.  Meter did not work for me, sending it back.