Pressurization is the creation of a false atmosphere in the cabin of the aircraft in order to allow us to breathe at higher altitudes without pure oxygen. The pressure of the cabin is usually around 8,000 ft but can be less according to how the system is set up. Pressurization happens in the engine, where hot air is compressed and then directed to the cabin. The compressed air is then cooled down, which makes it denser, on its way to the cabin. Once it reaches the cabin it is compressed enough to create an atmospheric pressure that mimics the desired altitude.