A danger detector, for example a flame detector, includes an alarm housing with an alarm cover. The housing part of the alarm cover is permeable to heat radiation in the central infrared range. A non-contact, optical heat radiation sensor which is sensitive to the incoming heat radiation and optically oriented to the housing part is arranged in the alarm housing. A processing unit for further processing a sensor signal emitted by the heat radiation sensor is mounted downstream of the heat radiation sensor. The processing unit is designed to monitor the signal emitted by the sensor with respect to significant fluctuations or flicker frequencies for open flames and to determine, based on a direct component of the signal emitted by the sensor, a temperature value for the ambient temperature in the surroundings of the danger detector. The heat radiation sensor may be a thermopile or a bolometer.