Abstract: A sensor module for detecting particulate matter of an aerosol, which may include a source of electromagnetic radiation and a collector for electromagnetic radiation. The collector may include a cavity and a first opening for the aerosol. The cavity may be reflective for the electromagnetic radiation. The first opening may allow exchange of the aerosol in and out of the cavity. The source of electromagnetic radiation may be arranged to project the electromagnetic radiation onto the aerosol which may be scattered as scattered electromagnetic radiation. The sensor module may include a detector of electromagnetic radiation arranged to detect the scattered electromagnetic radiation that is reflected by the collector. The source and the detector may be arranged on a same side of the collector. The source and the detector may be arranged at a same aperture of the collector.