Review on Accurate Temperature Humidity Detector Calibration: Ensuring High Quality by Peter Sullivan

The monitor displays 500 when switched on, regardless of the CO2 level in the environment. Leaving it in the same place but turning it on and off gives new readings that can vary by 200-500ppm. The outdoor reading was 500, which should have been 400-425. Temperature and humidity are normal. All in all, this device was a random number generator, so I returned it. I had high hopes for this beautifully built device but it is useless for CO2 monitoring. Note. I have professional experience in measuring CO2.