Product review (5 stars): Accurate and very quick readings
Seems accurate based on my reading.  The outdoor readings are consistently around 390 - 400ppm, despite the scare tactics employed by the climate change crowd.  Quite low in terms of the earth's history which has averaged 1500ppm and it has been as high as 7000ppm (Carboniferous Period - Google it).  I wanted to measure methods used to increase my CO2 levels in a small greenhouse. The menu is a not particularly intuitive and you must disable the alarm which is needlessly annoying.  Otherwise, I would recommend it .