Various embodiments may include fire detector comprising: a fire sensor generating a signal corresponding to a characteristic fire parameter; a control unit; and a photodiode for detecting ambient light in a spectrally delimited range of 400 nm to 1150 nm. The control unit analyzes the signal and generates a fire alarm if the signal corresponds to a predetermined threshold for a fire. The control unit analyzes a photo-signal received from the photodiode and if the flicker frequencies characteristic of open fire are detected, the control unit increases a sampling rate for acquiring the sensor signal from the fire sensor by reducing a filter time of an evaluation filter for the fire analysis and/or by lowering an alerting threshold.