The compressed air is passed through a pressure vessel with two "towers" filled with a media such as activated alumina, silica gel, molecular sieve or other desiccant material. This Desiccant Dryer material attracts the water from the compressed air via adsorption. A standard dew point that is expected by a regenerative dryer is −40 °C (−40 °F); this means that when the air leaves the dryer there is as much water in the air as if the air had been "cooled" to −40 °C (−40 °F). Required dew point is dependent on application and −70 °C is required in some applications.
