The One Step Calibration Kit is a simple and surefire method to accurately calibrate any digital or analog hygrometer or humidity sensor. The One-Step Calibration Kit utilizes Boveda’s 75.5% relative humidity standard, which is widely used and accepted by chemists and lab professionals to determine the accuracy of any hygrometer (also known as the “salt test”). Simply place your hygrometer inside the bag, close the zipper, and wait 24 hours. A perfectly-calibrated hygrometer will read 75% Rh. If your hygrometer reads above or below 75%, adjust the calibration by the number of percentage points it is off from 75%.