Why is my Micro+ showing a wrong ambient reading?
If the sensor has drifted or there was a previous miscalibration then you will need to perform a calibration reset as stated in the manual.
Ensure that the vent hole is not blocked and that the mouthpieces are attached properly during tests.
Ensure that the test is performed in a well ventilated area and no alcohol based products, VOC's, aerosols or room sprays are used on or in the presence of the device as these contaminations will affect the sensor within the device.
If the problem persists or has not been resolved by the information provided above, please contact Bedfont or your local distributor for more advice.