In general

The pressurization is the fact of maintaining with constant pressure a closed medium, independently of the external medium. In addition to the Aeronautical , many other fields are particularly consumers of this technology. For example, in a factory Agroalimentaire the whole of the line production is generally pressurized with a pressure slightly higher than that of outside, so that an open door does not let enter of germs the foodstuffs. Conversely, in an Atomic center , Biological or Chemical, where it is necessary to reduce any risk of dangerous matter escape, the buildings are pressurized with a slightly lower pressure with that of the external medium, so that no volatile substance can escape. One finds, always in the agroalimentary one, other applications of the pressurization for packing of chips, cakes or other food products likely to be found crushed: hermetic packing is pressurized with a pressure higher than the atmospheric pressure so that in the event of change of time, packing is not crushed on themselves, thus being likely to deteriorate the aspect of their contents.

Aeronautics

The pressurization is largely used in the Aéronautique civil and military: it consists in restoring an acceptable pressure by the human organism inside the Cockpit and/or of the cabin of the plane when this one flies to raised alttitudes, where the external conditions (- 50°C and 200 millibars of pressure, for example, i.e. the fifth of the atmospheric pressure on the ground), do not allow survival.

Its principle is simple: it consists in bleeding compressed air behind the compressor of the engine (or the turbomotor) for then partially slackening it and cooling it at the selected temperature and to send it in the cockpit or the cabin. One restores thus, partially at least, a pressure and a temperature acceptable for the pilots/the passengers of the Aéronef.

One does not completely restore the pressure of the ground, insofar as the cell of the aircraft would then support too great efforts in high-altitude, being likely to involve explosive decompression, where the cabin is emptied of its air violently by an opening caused by a shock with a foreign body or a too high interior pressure.