Pyroelectric sensor A measures the infrared radiation in the characteristic CO2 spectral range between 4.0 and 4.8 µm. Pyroelectric sensor B measures the infrared radiation of deceptive phenomena, such as hot objects, in the range between 5.1 and 6.0 µm. Sensor C is a silicon photo diode and measures solar radiation in the range between 0.7 and 1.1 µm A sensor measures the hot CO2 at a specific wavelength of the flame; the other two sensors measure interference radiation at other wavelengths at the same time. With the intelligent signal processing using fuzzy algorithms and wavelet analysis, the flame detector achieves excellent detection reliability with maximum immunity to interference emitters and sunlight at the same time. In order to safeguard against a possible decision emergency, the flame detector contains an additional emergency activation channel.