Abstract: A flame detection apparatus has a focused array based sensor which is responsive to radiation having a predefined wavelength for generating an image of the infrared radiation emitted within a monitored region, and means for measuring the spectral ratio of the intensity of radiation having a first wavelength emitted within the monitored region to the intensity of radiation having a second wavelength emitted within the monitored region. Processing means analyzes the output of the focused array based sensor and the spectral ratio measuring means for responses indicative of the presence of a flame within the monitored region.