“This is the first Instructable in the series: How to Make, Calibrate, and Test a Portable, Accurate, Low Cost, Open Source Air Particle Counter. The second installment, How to Build a Test Chamber for Air Particle Sensors, can be found here. The third installment, How to Build a Monodisperse Particle Generator for around $300, can be found here. This is a project by Rundong Tian, Sarah Sterman, Chris Myers, and Eric Paulos, members of the Hybrid Ecologies Lab at UC Berkeley. One of the most harmful airborne pollutants with respect to human health is particulate matter. Airborne particles with a diameter of less than 10 microns (PM10) pose an especially large risk: they can travel deeply into the respiratory system, causing a variety of cardiovascular and respiratory diseases.”