Abstract: The safety system comprises an electro-mechanical locking device (110) moveable between an unlocked position and a locked position. When the electro-mechanical locking device is in the locked position and is located on an energy isolation element (120) of a plant, energy is isolated at the isolation element. A mobile unit (130) is adapted to communicate with the electro-mechanical locking device in order to move the electro-mechanical locking device between the locked and unlocked position. When the electro-mechanical locking device is moved to the locked position a confirmation signal (260) is communicated to the mobile unit confirming that the electro-mechanical locking device is locked.