Air dryers remove moisture from the air.

Each dryer system- desiccant dryer, refrigerated dryer, and membrane dryer, uses its own technique.

The measurement of dry compressed air after processing is known as its 'dew point'. The lower the temperature of the dew point, the less amount of water vapor in the air. Dew point means the actual temperature where condensation begins. For example, if the dew point is -40 C° this means condensation starts only if compressed air temperature goes down to -40 C°.

FROM:https://www.atlascopco.com/en-us/