Particulate air pollution is separated into three classifications; coarse, fine and ultrafine particles. Coarse particles have a diameter of between 10µm and 2.5µm and settle relatively quickly whereas fine (0.1 to 2.5µm in diameter) and ultrafine (< 0.1µm in diameter) particles remain in suspension for longer. Our Respirable Dust Sampler AI-101 for PM10 sampling in ambient air uses the NEERI designed cyclone with sharper cut-off at 10 microns to separate the bigger particulates from the air stream before filtering it on the glass micro fibre filter.