Humidisorb Packets are filled with a self-regenerating desiccant that can absorb and release enormous quantities of moisture from surrounding air without becoming saturated. When first placed in service, a packet of granules will begin rapid absorption of moisture. The packet will absorb at least five to ten times more moisture than the conventional desiccant before coming to equilibrium with the relative humidity (RH) of surrounding air.

This will usually take several weeks to occur, even in very humid environments. During periods when the enclosure RH is lower than its long-term average the packet releases moisture in vapor form. The moisture desorption process cannot wet the air above its average RH level. When enclosure RH tends to rise above its average level, the packet absorbs moisture.

By absorbing moisture when the RH rises, and releasing some of the vapor phase moisture (regenerating) when the RH drops, the packet maintains a constant RH within the enclosure that is equal to the long-term average humidity.