Removing the water from the system is brought about by taking the vessel off line and depressurising quickly. Water held in the desiccant returns to the vapour phase, taking back the remaining latent heat and leaving the vessel with the bulk flow of air. Any remaining is flushed from the system by a purge of very dry air, taken from the outlet of the working column.
Compressed air switching between the columns, is by a completely driveless shuttle valve, activated by a change in differential pressure. Dew point is controlled by adjusting the purge of dry air passing counter current through the regenerating desiccant bed. The greater the flow the lower the Dew Point and the control of this purge, and thereby the Dew Point, is the most important feature of DRIAIR units greatly reduced operating costs.