Aerosols can be classified depending on their size [4]. PM10 (particulate matter) is understood to be the total volume of particles with an aerodynamic diameter 10 μm. These particles will pass through the nose and reach the lungs. The shape of the dust particles can be very complex with sharp edges and rough surfaces compared to a spherical shape. The aerodynamic particle diameter describes the sedimentation as well as deposition characteristics and health effects. Aim of most studies is the maximum allowable concentration of dust for the description of the impact on health and safety aspects in the workplace and not the impact on false alarms of optical smoke detectors. But many false alarms are caused by construction works in the surrounding of smoke detectors. For that reason several dust sources have been analyzed (see Table 1) in an extensive measurement campaign. The particle size distribution was measured by the HELOS analysis system by Sympatec Corporation. The HELOS system (Helium-Neon Laser Optical System) is using laser diffraction and analyzes particle size distribution by Fraunhofer diffraction. The system is shown in Fig. 1. During the measurements the aerosols are inserted in the measuring zone and exhausted by a cyclone. The insert is oriented vertically to the laser beam, which is diffracted by the aerosol. The diffraction patterns are measured by the system and converted to the particle size distribution. Important for the classification of the particle size are the cumulative distribution, volume distribution Q3 and the density distribution q3 [5] as a result of the measurement.