Carbon Dioxide Detector Indoor CO2 Monitor Bluetooth CO2 Meter Air Quality Monitor Meter Carbon Dioxide Digital Temperature and Relative Humidity Detector for Home Car Office Room (White)

have 3 therm pro readers which virtually match by .1 and i have 2 of these and they closely match temp and humidity of the tp co2 hcho and tvoc match up between 2 units very well but co2 measures around 420 ppm and i am about 15 inches away from them. have an extech co2 which has to be plugged into mains and that registers 700 when i am in room and more if i am close to it so dont think mobile ones too good on reading co2 thco and tvoc read 10 or less in my shop but hit 250 to 300 outside next to main road in rush hour. very nice display screen but just a bit dubious of the co2 measurement