Vacuum generation
Vacuum nature and quality - Contamination

Vacuuming or evacuating a working chamber or enclosure involves reducing (in principle, by elimination) the number of molecules in the various gases present in this volume.

At normal atmospheric pressure (1.01325.10 ⁵ Pa), in a one-liter volume at 0°C, there are 2.7.10 ²² molecules and atoms of gas. In a primary vacuum, i.e. at 10 ^-1 hPa, this still leaves 2.7.10 ¹⁸ molecules, or 99.99% empty. It is the nature of these remaining molecules (i.e. 2.7.10 ¹⁸ per liter) that is of interest to the operator, as they are sources...