When you first set up your humidor it will be empty. When you add cigars, they will immediately start drawing the moisture out of the atmosphere in the box. The humidity will naturally fall. The answer to this is to refresh – as described above – a couple of days after adding the cigars, or to add them a couple at a time rather than, for example, a dozen at once. You will also lose humidity by leaving the lid open for too long, so be sure to shut it quickly.