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Penetration of rod-shaped bacteria of different aspect ratios through filter media used in respiratory protection devices.

Qian Y; Willeke K; Donnelly J; Grinshpun SA; Ulevicius V
Proceedings of the AAAR 14th Annual Conference, October 9-13, 1995, Pittsburgh, Pensylvania. Mount Laurel, NJ: American Association for Aerosol Research, 1995 Oct; :14
The filter media in respiratory protection devices are currently tested with inert spherical test particles, such as corn oil particles. This represents the 'worst case" test since spherical particles are most penetrating. Today, health-care workers and hospital administrators are concerned about the presence of airborne antibiotic-resistant strains of the tuberculosis bacterium and the release of bacteria through the use of new medical technology, such as the carbon dioxide laser which may aerosolize viable tissues and cells. In this study, corn oil particles and different rod-shaped bacteria have been tested as to their collection efficiency. Four types of bacteria, Streptococcus salivarius, Bacillus megatherium, Pseudomonas fluorescens and Bacillus alcalophilis with aspect ratios (length to width) of 1.0, 2.6, 3.0, and 4.4 respectively, were generated with a six-nozzle Coilison nepulizer. These airborne bacteria were diluted with clean air to avoid agglomeration and were then passed through a Kr-85 charge neutralizer before reaching the test chamber. Masks of different filtration efficiency levels were tested in the chamber with the air flow rate per unit filtration area through each mask ranging from 86 to 427 cm/min-cm2. The concentrations of the airborne bacteria up-and down-stream of the masks were measured with an Aerosizer. This aerodynamic particle size spectrometer was found to size-differentiate bacteria down to about 0.5 um. The instrument was calibrated with the test bacteria prior to experimentation. It was found that all rod-shaped bacteria of similar aerodynamic size, but with aspect ratios larger than 1 penetrate less than the spherical bacterium streptococcus salivarius. For an aspect ratio of 4, the penetration of elongated bacteria is about half of the spherical ones. The penetration decreases as a function of aspect ratio for the same aerodynamic diameter. The filter penetration of spherical and rod-shaped bacteria increased with increasing flow rate for the masks tested.
Respirators; Respiratory-equipment; Respiratory-protection; Respiratory-protective-equipment; Filters; Particulate-dust; Bacteria; Airborne-particles; Health-care-personnel; Medical-personnel; Testing-equipment; Personal-protection; Personal-protective-equipment
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Proceedings of the AAAR 14th Annual Conference, October 9-13, 1995, Pittsburgh, Pensylvania
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University of Cincinnati, Cincinnati, Ohio
Page last reviewed: April 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division