PM10 Particles are often called coarse particles. They range in size from 2.5 to 10 microns. These particles can irritate the eyes and throat. People with respiratory issues like COPD, Asthma and allergies can experience heightened symptoms when they are exposed to these sized particle. These particles include pollen, large bacteria and wind blown dust. These particle need a MERV 11 filter or better for adequate control.