The Altec AIR HRL-0400-1-E6L, 400 SCFM Heatless Regenerative Desiccant Air Dryer is a large-capacity dryer that utilizes the pressure swing adsorption (PSA) drying process. The compressed air flows upward through the online (drying) tower where the water molecules adhere to the desiccant, where the residual water content of the compressed air is lowered to a pressure dew point (PDP) of -40°F or lower. Some of the dry air is also directed downward through the depressurized offline tower for the regeneration process. This dry air sweep desorbs water molecules from the surface of the desiccant and is exhausted to the atmosphere, preparing that tower for its next online cycle.