A DEVICE FOR MEASURING THE QUALITY OF AIR

A device for measuring the particle content of air comprises a laser source for generating laser light and for directing it to a target area, an air channel for directing the air subjected to the measurement as an air flow through the target area, and a light detector located adjacent to the target area for detecting bursts of light generated as the particles entrained with the air flow scatter the laser light in the target area. The device comprises a light trap between the laser source and the target area for reducing stray light propagating to the target area. The light trap comprises at least two intermediate walls which are substantially transverse in relation to the propagation direction of the laser light, each of the intermediate walls having an aperture for passage of a desirably limited amount of the laser light through the given intermediate wall. The intermediate walls are part of a same piece manufactured as one continuous block.