Desiccant Air Dryers are often called; regenerative, twin tower dryer, or adsorption dryers. These air compressor desiccant dryers all operate in a similar fashion. A "tower" is filled with activated alumina silica gel, molecular sieve, or other desiccant material. Water is attracted to these desiccant materials removing water from the air stream. Dew Points as low as -100 degrees Fahrenheit may be achieved. Generally, there is some type of purge air required. So, sizing desiccant air dryers is very important. Desiccant Air Dryers should always be considered when any of your compressed air equipment or piping is exposed to ambient temperatures lower than 38 degrees Fahrenheit.