Darth Vader's  Bio-Mechanical Suit

Darth Vader's grim black attire is a life-support system, his labored mechanical breathing the sound of a walking iron lung. Critically injured in a lightsaber battle with Obi-Wan Kenobi years ago, Vader became "more machine than man," kept alive only by the devices built into his suit. The fearsome visage of his breath mask reflects the dark identity that he assumed after his fall from the light side of the force.
Vader can only remove his mask in a special hyperbaric chamber, such as this one on board his Star Destroyer Executor. Allowing no one to assist him, Vader relies on mechanical devices to remove and replace his helmet and metal breath screen.