Regenerative desiccant dryers use a desiccant medium to remove moisture from the compressed air stream. Wet air passes directly through the desiccant medium, which then adsorbs the moisture. The desiccant medium has a finite capacity for adsorbing moisture before it must be dried out, or regenerated. To do this, the tower containing saturated desiccant medium is depressurized and the accumulated water is driven off using purge air, heat or a combination of both. Desiccant dryers are generally of a twin-tower construction, with each tower containing its own desiccant bed. This allows one bed to dry compressed air as the other undergoes regeneration. Regenerative dryers can achieve dew points of -40C to -70C and are a perfect solution when the air line goes outside during our cold Canadian winters.