The SMPS is being able to provide the size distribution and concentration of the fine fraction of the particulate in the size range 2 nm – 1 µm. It consists of three components in sequence: 1) a bipolar diffusion charger (model 3082, TSI) which confers a characteristic stationary charge distribution to the polydisperse particles by using a radioactive source (Kr-85); 2) a differential mobility analyzer column (DMA, model 3083, TSI) which separates the particles according to their electrical mobility by varying continuously the applied voltage within the column (Schmid et al., 2007); 3) a condensation particle counter (CPC, model 3750, TSI) where the classified monodisperse particles are counted after condensation of n-butanol on their surface.