Because hygrometers are small, they can be moved around in your house from lime to lime. Don't place your hygrometer near a radiator, a heat register or a chimney, or in any other location where it could be affected by direct heat. Remember that a hygrometer does not produce instant results. It may take up to two hours to provide a stable reading in a new location or to adjust to sudden changes in relative humidity. RH is percentage that indicates the amount of moisture in the air relative to the maximum amount the air can hold at that temperature.
Warm air can hold more moisture than cool air.
For exam pie, as a sample of air cools the RH rises. You should make sure that your hygrometer provides accurate readings. The technical term for this is calibration. When you calibrate your hygrometer, you are testing its accuracy by comparing it with an independent standard. All hygrometers should be calibrated.