AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
An Experimental Comparison of Aerodynamic and Optical Particle Sensing for Indoor Aerosols
PARICHEHR SALIMIFARD, Donghyun Rim, James Freihaut, The Pennsylvania State University
Abstract Number: 690 Working Group: Aerosol Physics
Abstract Particle size is one of the most influential factors in particle transport and human exposure. A number of studies have investigated the relationship between optical and aerodynamic particle size. However existing literature is inconclusive due to limited available data on particles with varying size distribution, shape, density, and optical characteristics. The objective of this study is to experimentally investigate the relationship between optical and aerodynamic sizing techniques for a wide range of biological and monodisperse particles.
Biological particles included cat fur, dog fur, Bacillus thuringiensis spore, pollen, dust mite and monodisperse particles involved silica, melamine resin, and methyl methacrylate in the range of 1- 10 µm. In addition, NIST indoor reference dust, quartz, and aluminum oxide particles were used as reference particles. Each particle was dispersed into a dispersion chamber (76×76×42cm) with a computer-controlled syringe injection system. Particle sizes and concentrations were simultaneously measured by aerodynamic particle sizer (APS3321, TSI) and optical particle counter (AeroTrak OPC, TSI).
Comparison between APS and OPC results showed that the relationship between optical and aerodynamic diameters strongly depends on the particle size itself for all tested particles with varying shape factors, density, and refractive indices. Generally, OPC measures a higher number count compared to APS in smaller size bins whereas as size bin increases this relationship is reversed. The cut point at which the inverse proportion of OPC and APS is happening increases from about 1 to 3 µm with respect to size of the tested particle. This study further discusses effects of density, shape and optical properties causing coincidence errors in aerodynamic and optical sensing -for each combination of the tested particles- resulting in disagreement between optical and aerodynamic size distributions. This finding implies that researchers should avoid interchangeable use of aerodynamic and optical particle sizing technique results without providing optical and aerodynamic parameters.