The term "pressure dew point" (PDP) is used to describe the water content in the compressed air. It is the temperature at which water vapor condenses into water at the current working pressure. Low PDP values indicate small amounts of water vapor in the compressed air. 

It is important to remember that atmospheric dew point can not be compared with PDP when comparing different dryers. For example, a PDP of +2˚C at 7 bar is equivalent to –23˚C at atmospheric pressure. To use a filter to remove moisture (lower the dew point) does not work. This is because further cooling leads to continued precipitation of condensation water.

You can select the main type of drying equipment based on the pressure dew point. When taking cost into account, the lower the dew point required, the higher the investment and operating costs for air drying. Five techniques exist for removing the moisture from compressed air: cooling plus separation, over-compression, membranes, absorption and adsorption drying.
Jiuzhou’s molecular sieve and activated alumina can be used in adsorption air dryer, and can reach the lowest PDP of -70℃
。