A scattered light detector for detecting particles, especially smoke particles in a test fluid, for use in an intake fire detection system, with - a test area which has a flow inlet and a flow outlet to form a flow path through which the test fluid can flow, - a light transmitter which emits a light beam in the direction of the emission, wherein the emitted light beam forms an overlapping area with the flow path, - a light receiver for receiving a scattered light component scattered at particles in the overlapping area, - a printed circuit board, wherein the light transmitter and the light receiver are connected to a front side of the printed circuit board facing the test area as surface-mountable components, and - the light receiver is arranged in such a way that a direct or indirect path of scattered light runs between the light receiver and the overlapping area, characterised in that - the test area is bounded by a test area wall, the test area wall having one or more recesses for accommodating optical components and/or for generating a plurality of light apertures, wherein - the light transmitter and the light receiver as well as the printed circuit board comprising the light transmitter and the light receiver are arranged outside the test area wall delimiting the test area, - the light beam transmitted by the light transmitter is guided into the test area by means of a fibre optic cable which deflects the light beam, the light beam entering the medium of the fibre optic cable and being passed on inside the latter, - the fibre optic cable opens out within one of the recesses of the test area wall, is received by one of the recesses or passes through one of the recesses, and - a light aperture or a non-reflective optical component is arranged within the direct scattered light path extending between the light receiver and the overlapping area and/or - the indirect path of scattered light extending between the light receiver and the overlapping area is formed by means of a fibre optic cable arranged within one of the recesses of the test area wall and in the field of view of the light receiver. - a test area which has a flow inlet and a flow outlet to form a flow path through which the test fluid can flow, - a light transmitter which emits a light beam in the direction of the emission, wherein the emitted light beam forms an overlapping area with the flow path, - a light receiver for receiving a scattered light component scattered at particles in the overlapping area, - a printed circuit board, wherein the light transmitter and the light receiver are connected to a front side of the printed circuit board facing the test area as surface-mountable components, and - the light receiver is arranged in such a way that a direct or indirect path of scattered light runs between the light receiver and the overlapping area, - the test area is bounded by a test area wall, the test area wall having one or more recesses for accommodating optical components and/or for generating a plurality of light apertures, wherein - the light transmitter and the light receiver as well as the printed circuit board comprising the light transmitter and the light receiver are arranged outside the test area wall delimiting the test area, - the light beam transmitted by the light transmitter is guided into the test area by means of a fibre optic cable which deflects the light beam, the light beam entering the medium of the fibre optic cable and being passed on inside the latter, - the fibre optic cable opens out within one of the recesses of the test area wall, is received by one of the recesses or passes through one of the recesses, and - a light aperture or a non-reflective optical component is arranged within the direct scattered light path extending between the light receiver and the overlapping area and/or - the indirect path of scattered light extending between the light receiver and the overlapping area is formed by means of a fibre optic cable arranged within one of the recesses of the test area wall and in the field of view of the light receiver.