BAR HARBOR — Emergency personnel from across Mount Desert Island responded to MDI Hospital on Wednesday for an oxygen leak in a large tank by the main entrance. According to hospital officials, a vendor was delivering oxygen when a valve broke, necessitating the need for immediate response. The Bar Harbor Fire Department positioned its trucks on either side of the building and drew water from nearby hydrants. Crews remained on scene for about a half hour while the oxygen emptied from the tank. Ambulances from Northeast Harbor and Southwest Harbor were also on scene.