An alarm system comprising at least one first signal source communicating with a central unit configured for providing a logically true alerting signal when predetermined conditions are met. The signal sources may include transponders and a confidential list containing the relation between an RFID chip and the name of the person identified may be stored in a computer. A verification unit is connected to independent signal sources and is configured for providing a logically true verification signal when predetermined conditions are met. The signal sources may also comprise means for measuring bio-functions, and the verification unit may be carried by a safety manager. In such a case, the safety manager will also be able to confirm or reject an alerting alarm from the central unit manually. An alarm signal is activated if and only if the alerting signal is true and the verification signal is true.