A safety device which detects personnel data of persons located in the detection zone thereof, said safety device operating continuously or in regular cycles and reporting to the central controller. The personnel data of all persons located in the longwall mine are stored in a central storage device of the central control and constantly compared to the detected personnel data. If a discrepancy arises between the saved personnel data and the detected personnel data, the central control unit executes a command which halts all functions of the excavation devices and interrupts all moving functions, said command being directed at the switching devices of the associated excavation devices.