A type of control used in situations such that a malfunction or unsafe condition results in a device, item of equipment, or process safely shutting down. An example is a gas burner where the fuel supply is automatically shut off in the event that the air (oxygen) supply should inadvertently cease. In contrast, a fail-to-danger is a fault or failure of a device or item of equipment that renders the plant in a dangerous condition such that a control system is unable to respond to provide the necessary protection.