A hermetically sealed pressure switch apparatus and method includes a metal bellows directly installed at an inlet port for providing hermetic sealing thereof. A spring (e.g. a wave spring) can be connected in parallel or series combination with the metal bellows. The metal bellows is capable of being extended when an input pressure is applied which in turn compress the wave spring. The compression of the spring transfers a required motion to a plunger associated with an electrical switch in order to actuate the electrical switch when a certain pressure relative to a perfect vacuum is attained. The metal bellows and the spring can be pre-compressed utilizing the plunger in order to maintain switch set point accuracy and spring stiffness.