Abstract: Various embodiments include a fire or smoke alarm comprising: a detection arrangement arranged within an alarm housing; and an alarm-housing cover having, on an inner side, a plurality of housing ribs pointing radially in the direction of an alarm dome. The detection arrangement comprises a level divider with an opening. A maximum possible spacing between two points on a peripheral line of the opening or on a common peripheral line of a plurality of openings is larger than a diameter of the alarm dome. The peripheral line of the opening or the common peripheral line of a plurality of openings in the level divider extends beyond the alarm dome of the alarm-housing cover on all sides.

Abstract: Various embodiments include a scattered light smoke detector comprising: a two-color LED for emitting light of a first wavelength and a second wavelength; a photosensor spectrally matched with said two-color LED; and a control unit connected to the two-color LED and to the photosensor. The control unit is configured to control the two-color LED to emit light of the first wavelength or the second wavelength and to detect a photosensor signal of the photosensor. The control unit is further configured to analyze the photosensor signal for a first scattered radiation intensity and a second scattered radiation intensity allocated respectively to the first wavelength and the second wavelength. There is a polarizer optically connected upstream of the photosensor or downstream of the two-color LED. The polarizer polarizes light passing through at different intensities in dependence upon the respective wavelength of said light.

Abstract: Various embodiments include a fire or smoke alarm comprising: a detection arrangement arranged within an alarm housing; and an alarm-housing cover having, on an inner side, a plurality of housing ribs pointing radially in the direction of an alarm dome. The detection arrangement comprises a level divider with an opening. A maximum possible spacing between two points on a peripheral line of the opening or on a common peripheral line of a plurality of openings is larger than a diameter of the alarm dome. The peripheral line of the opening or the common peripheral line of a plurality of openings in the level divider extends beyond the alarm dome of the alarm-housing cover on all sides.

Abstract: Various embodiments include a scattered light smoke detector comprising: a two-color LED for emitting light of a first wavelength and a second wavelength; a photosensor spectrally matched with said two-color LED; and a control unit connected to the two-color LED and to the photosensor. The control unit is configured to control the two-color LED to emit light of the first wavelength or the second wavelength and to detect a photosensor signal of the photosensor. The control unit is further configured to analyze the photosensor signal for a first scattered radiation intensity and a second scattered radiation intensity allocated respectively to the first wavelength and the second wavelength. There is a polarizer optically connected upstream of the photosensor or downstream of the two-color LED. The polarizer polarizes light passing through at different intensities in dependence upon the respective wavelength of said light.