Five years' testing has demonstrated that little or no drying takes place in a tower. Drying occurs at the mix point of seed cotton and hot air. High air velocities at the mix point enhance not only drying but also cleaning. The only change, if towers are removed and fans slowed to maintain air flow, is decreased power consumption. Energy savings will, usually in one ginning season, pay for high efficiency fans and the engineering studies needed to size them optimally.