Traditionally, the cleaning process was carried out at centralized factories; high street cleaners’ shops received garments from customers, sent them to the factory, and then had them returned to the shop, where the customer could collect them. This was due mainly to the risk of fire or dangerous fumes created by the cleaning process. At this time, dry cleaning was carried out in two different machines—one for the cleaning process itself and the second to dry the garments.
Machines of this era were described as vented; their fumes and drying exhausts were expelled to the atmosphere, the same as modern tumble-dryer exhausts. This not only contributed to environmental contamination but also much potentially reusable perc was lost to the atmosphere. Much stricter controls on solvent emissions have ensured that all dry cleaning machines in the Western world are now fully enclosed, and no solvent fumes are vented to the atmosphere. In enclosed machines, solvent recovered during the drying process is returned condensed and distilled, so it can be reused to clean further loads or safely disposed of. The majority of modern enclosed machines also incorporate a computer-controlled drying sensor, which automatically senses when all detectable traces of perc have been removed. This system ensures that only the smallest amount of perc fumes will be released when opening the door at the end of the cycle.