8 EJECTORS AND MECHANICAL VACUUM SYSTEMS
Industry has grouped pressures below atmospheric level into :
|Range of Pressure|
|Rough vacuum||760–1 torr|
|Medium vacuum||1–0.001 torr|
|High vacuum||0.001–10−7 torr|
|Ultra-high vacuum||10−7 torr and below|
Rough vacuum is used in about 90% of the chemical, petrochemical, and other processing industries. This range generally includes vacuum distillation, filtration, crystallization, drying, reaction, and others. Medium vacuum is most applicable to molten metals degassing, molecules distillation, freeze drying, and others. High and ultra-high ranges are most useful for thin films, research, and space simulation.
For reference, note that the unit of vacuum measurement is torr.