Measurements and Factorial Analysis of Micron-Sized Particle Adhesion Force to Indoor Flooring Materials by Electrostatic Detachment Method

2013

Resuspension is an important source of indoor particles and the amount of dust loading is an important factor in resuspension emission rates. Field studies have shown that light to heavy dust loads can be found in the indoor environment, on both the surfaces of flooring and ventilation ducts. These diverse particle deposits can be broadly classified as either a monolayer, in which particles are sparsely deposited on a surface, or a multilayer, in which particles are deposited on top of one another and there is particle-to-particle adhesion and interaction. This experimental wind tunnel study explores the role of the type of particle deposit on aerodynamic resuspension from linoleum flooring and galvanized sheet metal. Resuspension fractions are reported for both monolayer and multilayer deposits exposed to a wide range of air velocities. The type of particle deposit is found to strongly influence resuspension. In general, the results show that resuspension from multilayer deposits can occur at significantly lower velocities compared with monolayer deposits. For example, resuspension fractions at an air velocity of 5 m/s for the canopy layer of multilayer deposits were similar to those found for monolayer deposits at 50 m/s. Additionally, for multilayer deposits, resuspension fractions for the canopy layer increased with increasing dust load and negligible resuspension occurred along the surface layer. It was found that the relationship between the particle deposit height and the viscous sublayer thickness of the airflow can help explain the differences in resuspension that were observed between the two types of deposits. The impact of the type of particle deposit on

Section: Limitations Of the Present Investigationmentioning

confidence: 99%

Wind Tunnel Study on Aerodynamic Particle Resuspension from Monolayer and Multilayer Deposits on Linoleum Flooring and Galvanized Sheet Metal

Boor

2013

“…In order for resuspension to occur, the adhesion force binding the substrate and particles must be overcome (Corn 1961). Hu et al (2008), in their measurements of adhesion forces between 1 µm alumina particles and bacterial spores and vinyl and rubber indoor flooring materials, found the actual area of contact between particles and surfaces is less than the theoretically ideal contact area for indoor surfaces. Differences in substrates, particularly microscale surface roughness, are therefore likely to affect resuspension.…”

Section: Discussionmentioning

confidence: 99%

Impact of Airflow Characteristics on Particle Resuspension from Indoor Surfaces

Mukai

2009

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 resuspension, 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 galvanized 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.

“…Full-scale walking-induced resuspension studies have reported resuspension from both monolayer (Karlsson et al 1999;Tian et al 2011) and multilayer deposits Kubota et al 2009;Tian et al 2011;Shaughnessy andVu 2012, Kubota andHiguchi 2013) on hard flooring. Gomes et al (2007) found aerodynamic removal forces associated with airflow disturbances generated by human walking to be the primary mechanism for particle resuspension from flooring, although surface vibrations, mechanical abrasion, and electrostatic forces can contribute to resuspension (Gomes et al 2007;Hu et al 2008;Qian and Ferro 2008;Hubbard et al 2012). Several studies investigated the airflow generated by foot motions.…”

Section: Hard Flooringmentioning

confidence: 99%

Monolayer and Multilayer Particle Deposits on Hard Surfaces: Literature Review and Implications for Particle Resuspension in the Indoor Environment

Boor

2013

Particle deposits on indoor surfaces can be as complex and diverse as the indoor environments in which they exist. Dust loading can range over several orders of magnitude, suggesting the existence of different types of particle deposits. These deposits can be broadly classified as either a monolayer, in which particles are sparsely deposited on a surface, or a multilayer, in which particles are deposited on top of one another and there is particle-toparticle adhesion and interaction. Particles within these diverse structures of settled indoor dust can become airborne through a process known as resuspension, which can occur due to airflow in ventilation ducts or human activity indoors. The dust loading and deposit structure on an indoor surface may have important implications for resuspension in the indoor environment. This literature review provides a summary of dust loads found on indoor surfaces in field studies and classifies each dust load as either a monolayer or multilayer particle deposit. The article highlights the unique attributes associated with resuspension from both types of particle deposits by summarizing key findings of the experimental resuspension literature. The fundamental differences in the resuspension process between monolayer and multilayer deposits suggest that resuspension may vary considerably among the broad spectrum of dust loads found on indoor surfaces.