Impact of Airflow Characteristics on Particle Resuspension from Indoor Surfaces

This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Resuspension is an important source of indoor particles. We measured the resuspension of 1 to 20 µm particles on common indoor materials and explored the importance of turbulence to the resuspension process. Experimental variables included materials (linoleum, carpet, and galvanized sheet metal) and bulk air velocity (5, 10, 15, 20, and 25 m/s). At each of these conditions the turbulence intensity in the boundary layer was varied between a low, medium, and high state and ranged from 9 to 34% at the surface. For comparison of resuspension from the considered surfaces and at different flow conditions, we use the relative resuspen-sion, which quantifies resuspension without requiring knowledge of the number of particles initially seeded on the surface. The relative resuspension compares the fraction of particles resuspended at the experimental conditions to the maximum achieved with a controlled impinging jet. In general, the results show that for the ranges considered, increasing velocity caused the largest increase in resuspension, followed by increasing turbulence intensity and then increasing particle diameter. All three material types showed consistent patterns with carpet having the largest resuspension for a given set of conditions, followed by linoleum and then by gal-vanized sheet metal. High turbulence and high velocity conditions minimized the differences between materials. An understanding of the relative magnitudes of these effects allows for better analysis and mitigation of indoor resuspension. INTRODUCTION The term resuspension refers to a phenomenon in which particles, initially on a surface, join the passing fluid stream. Resuspension is important for several manufacturing processes, healthcare delivery systems, radionuclide transport, and geological systems (i.e., Sehmel 1980), but also acts as a source of