Our desiccant dryer is a dual column dryer filled with aluminum oxide pellets in both columns. Each column is equipped with a timer where one column is pressurized with an internal temperature at -40 degrees Fahrenheit. The other column is under 0 pressure to expel the water vapor from the pellets. When the column timer alternates each column, it releases moisture build up to then allow the second column to begin the process of filtering the air. NOTE: Your air dryer cfm capacity needs to be 15% larger than the air compressor cfm output to maintain the cycles of the dryer.