The refrigerant dryers uses an refrigerant gas in order to cool the compressed air and then remove the water condensate from the air, with this technic we can reach MAX. 3°C. PDP. An adsorption dryer, use an " adsorption material called desiccant " in order to remove ( adsoprb ) the humidity on the compressed air. With this method we can reach a PDP < 3°C. ( -40°C. or -70°C.). Depending on which dryer and option the customer chooses to use.
An adsorption dryer is required to be used when the ambient temperature goes under ZERO °C, to avoid ice building in pipes and applications.