Scattered light smoke detector with a two-colour light emitting diode

A scattered-light smoke detector includes a detector unit that operates according to the scattered-light principle. The detector unit includes a light-emitting diode (LED) to irradiate particles to be detected and a spectrally sensitive photosensor to detect the light scattered by the particles. The LED and photosensor are aligned such that a principal optical axis of the LED and a principal optical axis of the photosensor define a scattered-light angle. The LED includes a first and a second LED chip for emitting first and second light beams with light in a first wavelength range and a different second wavelength range, and an LED chip carrier arranged orthogonally to the principal optical axis. The two LED chips are arranged side-by-side on the LED chip carrier. The LED is rotated such that a chip axis extending through the two LED chips is orthogonal to an angle plane defined by the two optical axes.