A tube is filled with hollow membranes that allow compressed air to pass but remove water vapor. These dryers give a -80degree F dew point relative to the incoming air temperature. Membrane dryers have NO MOVING PARTS and require NO ELECTRICITY & MAINTENANCE, and therefore have a very long life. It occupies 1/10th of the space as compared to other dryers. There are many model of the membrane module which depends upon its size and capacity. A combination of many such modules enhance the capacity and dew point.