Adsorption dryers achieve their drying effect through pressure changes (pressure swing adsorption principle).
Since air's capacity to hold moisture is inversely proportional to its pressure, a portion of the dried air (called regenerated air) is depressurized and expanded to atmospheric pressure. This pressure change dries the expanded air further. This regenerated air then flows through a layer of desiccant that needs regeneration (i.e., a drying tower that has already absorbed sufficient moisture) that is not connected to the airflow. The dried regenerated air draws moisture from the desiccant and carries it out of the dryer, achieving dehumidification. The two towers operate in a cycle, requiring no heat source, and continuously supply dry compressed air to the user's air supply system.