My recommendation can be deduced from simple physics: damp air is lighter than dry air, and will therefore rise. As a matter of principle, the relative air humidity in the immediate area of the humidification system is always higher than in the rest of the humidor, since the humidification system is responsible for evaporating water.
Consequently the distance between the cigars and the humidifier should be as great as possible. The following recommendations are based on the size of the humidor, the presence (or not) of a tray and the kind of humidifier:
Humidor with no tray
In this case the humidifier can easily be placed in the lid to create maximum distance between it and the cigars. If you are using an active (electronically regulated) humidifier, this should include a fan, so that the air is blown down into the humidor and the relative air humidity measured in the air sucked into the humidifier. If the humidor contains a large number of cigars, they should be covered with a cedarwood veneer so that the humid air expelled by the humidifier is not blown directly onto the cigars.
Humidor with tray
The problem with most humidors containing a tray is their faulty design. If cigars are placed on the tray and block the few airholes in it, how is it possible for the humidified air to circulate from the top to the bottom of the humidor (or vice-ver-sa)? For this reason I make the following suggestion: If you have a badly made tray, use two humidifiers (one in the lid, and one at the bottom of the humidor). If you have two separate trays with sufficient room between them, or a well-designed tray that permits adequate circulation of the air, then the humidifier should be placed in the bottom of the humidor in order to maintain even humidity.
This article was published in the Cigar Journal Spring Edition 2011. Read more