Vacuum – Definition

A vacuum is defined colloquially as the state encountered in a room at pressures below atmospheric pressure. These pressures can be generated by gases or vapors that are evenly distributed over the room.

The standard definition of vacuum is “the state of a gas at which its pressure in a vessel and therefore its particle density is lower than that of the ambient surrounding atmosphere or in which the pressure of the gas is lower than 300 mbar, i. e. lower than the pressure of the atmosphere on the Earth’s surface.“