Roughing pump

A roughing pump is any vacuum pump (typically mechanical) used to initially evacuate a vacuum system, as a first stage towards achieving high vacuum or ultra high vacuum. The term "roughing pump" derives from the vacuum range it works in, "rough vacuum", above 1x10 torr. Pumps that operate in the high vacuum ranges typically don't operate, or only operate inefficiently, at atmospheric pressures, whereas pumps that work efficiently at atmospheric pressure usually cannot produce a vacuum lower than approximately 1x10 torr.