A surveillance system having surveillance terminals and a surveillance center is configured to perform effective hazard alert signaling, depending on the hazard type. The surveillance system comprises a plurality of surveillance terminals, which are connected to the surveillance center by a network, carries out hazard and alert signaling. One surveillance terminal detects a hazard and sends a hazard information signal reporting what hazard has just been detected to the surveillance center. The surveillance center receives the hazard information signal, identifies what type of hazard source and the surveillance terminal that sent the hazard information signal, selects surveillance terminals to be alerted to the hazard from among the plurality of surveillance terminals, depending on the identified type of the hazard source and its locality, and sends a hazard alert signal to the selected surveillance terminals.