Multisensor fire detector with integrated smoke detector, heat detector and gas sensor (CO) with enhanced false alarm management, for preventive and early detection of deep-seated smouldering fires which give a lot of CO as well as flaming fires through combined evaluation of scattered light, temperature and gas. An alarm is actuated at carbon monoxide (CO) concentration levels that are life-threatening for humans. Less susceptible to false alarms caused by dust, as well earliest and reliable detection of fire development due to the additional detection of CO. Also a Technical Alarm (TAL) can be programmed with the flexible programmable CO threshold up to 150 ppm. The detector is provided with an integrated isolator. A remote indicator can be connected.