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Use of acoustical energy for particle resuspension.

Authors
Azadi-S; Afshari-A; Frazer-D
Source
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida. Fairfax, VA: American Industrial Hygiene Association, 2000 May; :21
NIOSHTIC No.
20020879
Abstract
Aerosol generation is a common task in many applications, such as calibration of light scattering and particle characterizing instruments. Commercially available instruments can generate aerosols from soluble material in liquid form, and most are effective for particles under 2 microm. Not all materials are soluble, however, and resuspension of particles from powder samples is often desired. The goal of this study was to design a system for aerosolizing powder of any size. The system was to be simple, inexpensive and effective over a large range of sizes. An acoustical generator was designed and constructed using a 6.5-in. speaker set in a support base. A 4-in. diameter aluminum tube was closed off at both ends with latex rubber-dam material and was constructed to fit tightly over the support base. The speaker was excited with a 4- V RMS signal that slowly varied over a frequency range between 20 Hz and 30 Hz. The generated sound waves vibrated the latex material, which in rum vibrated the air column and the particles inside the tube. Dry microsphere standards with known aerodynamic diameters, a density of 1.05 g/mL, and a refractive index of 1.59 at 589 nm (25C) were used. A feeding system introduced the particles into the chamber using HEPA-filtered compressed air pulses. Airflow through the system was maintained at 5 L/min. The input air was passed through a dryer column, a HEPA filter to retain any particles, and a deionizer system to reduce the electrostatic charge on test particles inside the chamber. A variety of standard particles of known aerodynamic diameters in powder form were aerosolized using the acoustical generator, and samples were analyzed using an aerodynamic particle sizer (APS). The APS results indicated that the generator is capable of resuspending powder of different size particles, and can be used as a calibrating instrument.
Keywords
Aerosols; Aerosol-generators; Sampling; Aerosol-sampling; Aerosol-particles; Air-monitoring; Air-sampling; Air-samples
Publication Date
20000520
Document Type
Abstract
Fiscal Year
2000
NTIS Accession No.
NTIS Price
NIOSH Division
HELD
Source Name
American Industrial Hygiene Conference and Exposition, May 20-25, 2000, Orlando, Florida
State
WV; FL; VA
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