Resuspension of Dust Particles in a Chamber and Associated Environmental Factors

Abstract

Experiments investigating particle resuspension from human activities were conducted in a full-scale experimental chamber. The experiments tested three types of flooring (vinyl tiles, new and old level-loop carpets) and two ventilation configurations (ceiling and side wall supply systems). The floorings were seeded with 0.1-10 µm test particles. The airborne particle concentration was measured by an array of optical particle counters (OPCs) in the chamber. Resuspension rates were estimated in size ranges of 0.8-1, 1.0-2.0, 2.0-5.0, and 5.0-10 µm ranging from 10 −5 -10 −2 hr −1 , with higher resuspension rates associated with larger particles. Resuspension via walking activity varied from experiment to experiment. "Heavy and fast" walking was associated with higher resuspension rates than less active walking, most likely due to a combination of increased pace, increased air swirl velocity, and electrostatic field effects established by the walking. The type of floorings also influenced the particle resuspension. Given the same size and mass distribution of test particles per unit floor area, resuspension rates for the seeded new level-loop carpet were significantly higher than those for the vinyl tile flooring for larger particles (1.0-10 µm) under the ceiling air supply system. INTRODUCTIONAs summarized by Lioy et al. (2002), settled dust is dominated by particles smaller than 500 µm; the most frequently identified components in house dust are skin, soil, starch, hair, cotton, and plant material (>85% of samples); and the second most frequently identified components are fungal material, synthetic fibers, polymers, paint, and metals. Specific toxicants identified in dust include semivolatile and non-volatile pesticides, polycyclic aromatic hydrocarbons (PAHs), heavy metals,

Large Eddy Simulation of Particle Re-suspension During a Footstep

“…They showed the details of transient particle re-suspension and dispersion in the room and were able to predict overall re-suspension rates, but the removal of particulates from the carpet layer was idealized solely as a mass displacement effect. Predicted re-suspension rates ranged from 3.7 × 10 -5 to 8.1 × 10 -5 s -1 for two size classes of particles (2.7 and 7.7 µm), which is slightly greater than other experiments (Gomes et al 2007;Qian and Ferro 2008); however, the total particle number concentrations at several locations showed reasonably good agreement with experimental data (Rosati et al 2008).…”

“…The details are summarized in Table 3. Figure 16 shows a comparison of the predicted re-suspension rates for different particle sizes with those in experiments (Gomes et al 2007;Qian and Ferro 2008) and the numerical simulation (Oberoi et al 2010). Recent experiments showed that average re-suspension rates ranged from 10 -5 to 10 -2 h -1…”

“…Qian and Ferro (2008) estimated re-suspension rates due to human activities under various environmental conditions. Short-term responses of particle re-suspension were characterized with average re-suspension rates ranging from 10 -5 to 10 -2 h -1 for particles with sizes of 0.8-10 µm.…”

“…Human activities are found to be an important factor for particle re-suspension in indoor environments (Thatcher and Layton 1995), and precise estimates of re-suspension rates due to human activity may be necessary to quantify potential risk effects. Previous experimental studies (Thatcher and Layton 1995;Karlsson et al 1996Karlsson et al , 1999Ferro et al 2004;Gomes et al 2007;Qian and Ferro 2008;Rosati et al 2008) of particle re-suspension under the influence of human activities have attempted to estimate overall re-suspension rates as a function of particle sizes, substrate conditions, and patterns of human activity. As examples, Gomes et al (2007) initiated complex floor disturbances such as floor vibrations and air swirling to explore mimic human-motion effects on particle re-suspension.…”

Conceptual model for assessment of inhalation exposure to manufactured nanoparticles

“…Experiments on resuspension caused by human indoor activities, such as walking and cleaning, have focused on particles B1 mm. In general, the resuspension rate increases with increasing particles size from 1 mm to over 10 mm (Qian and Ferro, 2008). Therefore, human activities may cause resuspension of manufactured nanoparticles attached to super-micron particles.…”