Corporate Buyers Guide

There are several regimes of vacuum. These regimes refer to how close the vacuum approaches a perfect vacuum. A perfect vacuum has no particles in it and is impossible to create. The vacuum that we can use is called partial vacuum. Even the vacuum of interstellar space has a few particles per cubic centimeter. The quality of the vacuum is measured with pressure. The most common unit for pressure is the torr, named after Torricelli who the first to measure and describe atmospheric pressure. One torr was originally equal to one millimeter of mercury, now it is defined as 1/760 of atmospheric pressure.

The regimes of vacuum are low vacuum, medium vacuum, high vacuum, and ultra high vacuum. Low vacuum is also known as rough vacuum. A low vacuum is any vacuum from atmospheric pressure, 760 torr, down to one torr. Low vacuum is the easiest to produce. Medium vacuum is any vacuum from one torr down to 10^-3 torr. Most vacuum ovens only go down to medium vacuum. High vacuum is any vacuum from 10^-3 torr down to 10^-8 torr. Ultra high vacuum is any vacuum below 10^-8 torr. This is the realm of particle accelerators. At low and medium vacuum, the remaining air still behaves as a fluid, at high and ultra high, it behaves like a bunch of billiard balls. Vacuum ovens are not usually designed for use at positive pressure, that is pressure over atmospheric pressure.