A low-cost particle counter as a realtime fine-particle mass monitor

Exposure to particles with aerodynamic diameters less than 2.5 mu m is estimated to cause significant morbidity and mortality worldwide leading many countries to develop ambient air pollution standards and guidelines. At local scales, community and environmental justice groups are also concerned about PM2.5 concentrations that may be elevated above regional concentrations typically measured by centrally located monitors and standards as well. In an attempt to develop a low cost, easy to use monitor we evaluated a low-cost optical particle counter, the Dylos (TM), as a fine particulate mass sensor. Modified into a system called the Berkeley Aerosol Information Recording System (BAIRS), we compared performance against standard commercial instruments in chambers using polystyrene latex spheres, ammonium sulphate, and woodsmoke and in an urban ambient setting. Overall we find that the limit of detection of the BAIRS is less than 1 mu g m(-3) and the resolution is better than 1 mu g m(-3) for PM2.5. The BAIRS sizes small (<0.5 mu m) particles, and is able to accurately estimate the mass concentration of particles of varying composition including organic, inorganic, and ambient particles. It is able to measure concentrations up to 10.0 mg m(-3). In an ambient roof-top test of the BAIRS and a more expensive commercially available light scattering particle monitor the BAIRS response tracked well with the commercial monitor and daily means were within 80% of each other. We conclude that with appropriate modification the system could be developed into an accurate low cost realtime particle mass monitor for use in a wide range of applications.