Engineers working in air quality and air pollution often need to characterize the size distribution of aerosols. Two of the more commonplace methods for determining particle size distributions are the electrical sensing zone method and the time- of-flight method. The two methods have been compared for regularly shaped particles. Agricultural applications typically involve irregularly shaped particles. This study compared the two methods for two irregularly shaped dusts – Arizona Road Dust with mass mean diameters of 2.5 µm and 10 µm.

Both methods have their advantages, particularly the ability to sample real time with the APS and the ability to analyze large numbers of samples after collection by the Coulter Method. The differences between the sizes reported were insignificant for many applications where the natural variability in the data in much greater than the difference between the instruments. More work needs to be done on developing shape factors to compare the two instruments and possible shape factors to compare to an absolute standard, such as a gravitational settling method.