Surface holding magnets are suitable for securing doors in an electro-magnetic system. They are easy to install, as there is no need to make modifications or cut-outs in door frames. A written communication from the DIBt, the German Center of Competence in Civil Engineering, dated March 24, 1991, states that electro-magnets may also be used on fire doors. Surface holding electro-Magnet 828 contains an integrated contact to monitor locking status (Hall effect sensor).