A barrier of a vacuum pump prevents contamination from entering a vacuum pump air line. The barrier separates parts of the pump and is moveable between an initial state and a distended state. The barrier is assembled within the pump with a pre-load. When the vacuum source is applied to the barrier, the barrier achieves a distended state and when the vacuum source is released, the barrier incrementally self returns to an initial state. The geometry and material construction of the barrier, along with the pre-load, assists in returning the barrier on its own to the initial state from the distended state.