Ingersoll Rand desiccant dryers are designed to eliminate costly production interruptions which can result from moisture. All of the dryers use twin desiccant towers and strategically positioned valves for drying compressed air. The basic difference between the two dryer technologies is the manner in which moisture is desorbed from the desiccant, also known as regeneration. Heatless dryers use compressed air to purge the towers of moisture while heated blower dryers utilize externally heated ambient air. Heatless dryers are lower in capital investment, but may be more expensive to operate because they require a portion of the dried compressed air to be diverted from the air system for desiccant regeneration. Heated blower dryers require the highest initial capital investment due to the centrifugal blower, but with little or no diversion of compressed air from the system for regeneration, they offer significantly lower operating costs.