In this work, we present M-DUST, a novel low-cost and real-time smart monitoring sensor for Particulate Matter (PM) emission measurement. It is based on the Tyndall scattering process to count particles concentration. A comparison on different methods to evaluate particles concentration has been discussed. A mechanical filter is used to select the particulate matter with the appropriate cut-off aerodynamic diameter. The presented device is an intelligent sensor thanks to its features, such as: ability to make self-diagnosis, self-adaptation and transparency to communication interface. Tests are carried out in the Italian city of Taranto by using non-toxic substances and analysis chamber.