during the drying cycle, the garments are tumbled in a stream of warm air (60-63°c/140-145°f) that circulates through the basket, evaporating any traces of solvent left after the spin cycle. the air temperature is controlled to prevent heat damage to the garments. the exhausted warm air from the machine then passes through a chiller unit where solvent vapors are condensed and returned to the distilled solvent tank. modern dry cleaning machines use a closed-loop system in which the chilled air is reheated and recirculated. this results in high solvent recovery rates and reduced air pollution. in the early days of dry cleaning, large amounts of perchlorethylene were vented to the atmosphere because it was regarded as cheap and believed to be harmless.