Product review (1 stars): Needs a fan
Out of the box, the hygrometer was off by 11% compared to others I have. I pulled out a NIST calibrated wet bulb / dry bulb thermometer to make sure it was no where near right, and it was confirmed. I put the unit in front of the fan used for the NIST measurement, and it started closing the difference to accurate after about 30 minutes. I guess it needed to be blown out? No, after setting it on a counter away from a fan, it went back to being off. Interestingly enough the thermometer measurement was also all over the place. Obviously the unit is primarily for CO2. I found similar measurement instability there too. The solution appears to be to keep a fan on it. I have a Dylos DC1100 particle counter that has one integrated, and my conclusion is this unit needs one too.