Particulate matter smaller than 2.5 micrometers (PM2.5) can enter and reside in the human lungs and long term exposure can cause a wide range of negative health effects. The existing monitoring instruments are bulky and expensive, not suitable for monitoring indoor air quality and personal PM2.5 exposure levels. The goal of this project is to develop a low-cost MEMS-based device capable of sizing and measuring PM 2.5 concentration in real-time to provide an instantaneous air quality reading to the user. The project consists of two main components: the particle separator and the particle detector.