Fire detector

The fire alarm (1) comprises a light source (7), measuring chamber (9) and a light receiver (8), all housed within an optical module (5). A temperature sensor (13) and the light receiver (8) are both connected to an evaluation electronic module (6). A sensor (12) for combustion gas, e.g. CO, is additionally provided. The electronic module (6) comprises a fuzzy logic controller, which compares the output signals of individual sensors (5,12,13) and determines the type of fire. For each type of fire a different application specific algorithm is selected. The fuzzy logic associates smoke concentration with combustion gas concentration and with a parameter formed from the gradients of temperature and of smoke gas.