The FHD series heated adsorption air dryer provides dry air with a pressure dew point of -40 ° C. The design is oriented towards energy saving, with a patented internal heat re-utilization device. This dryer contains twin chambers, each filled with desiccant material which dries the compressed air as it passes through. One chamber is operational (drying), while the opposite chamber is regenerating. Temperature controls are used to stop heating in advance, and the “waste” heat is reused for regeneration during the cooling process. Twenty percent of regeneration energy is saved.