Evaluation of Nano- and Submicron Particle Penetration through Ten Nonwoven Fabrics Using a Wind-Driven Approach

Abstract

Existing face mask and respirator test methods draw particles through materials under vacuum to measure particle penetration. However, these filtration-based methods may not simulate conditions under which protective clothing operates in the workplace, where airborne particles are primarily driven by wind and other factors instead of being limited to a downstream vacuum. This study was focused on the design and characterization of a method simulating typical wind-driven conditions for evaluating the performance of materials used in the construction of protective clothing. Ten nonwoven fabrics were selected, and physical properties including fiber diameter, fabric thickness, air permeability, porosity, pore volume, and pore size were determined. Each fabric was sealed flat across the wide opening of a cone-shaped penetration cell that was then housed in a recirculation aerosol wind tunnel. The flow rate naturally driven by wind through the fabric was measured, and the sampling flow rate of the Scanning Mobility Particle Sizer used to measure the downstream particle size distribution and concentrations was then adjusted to minimize filtration effects. Particle penetration levels were measured under different face velocities by the wind-driven method and compared with a filtration-based method using the TSI 3160 automated filter tester. The experimental results show that particle penetration increased with increasing face velocity, and penetration also increased with increasing particle size up to about 300 to 500 nm. Penetrations measured by the wind-driven method were lower than those obtained with the filtration method for most of the fabrics selected, and the relative penetration performances of the fabrics were very different due to the vastly different pore structures.

Keywords:

• nanoparticle penetration
• nonwoven fabric
• protective clothing

ACKNOWLEDGMENTS

The authors gratefully acknowledge Dr. Zhong-Min Wang currently with the California Department of Public Health for conducting some preliminary experiments; Mr. Venugopal Boppa at North Carolina State University for measuring physical properties of the fabrics; Dr. Samy Rengasamy at NIOSH, Mr. Jeffrey Stull at International Personnel Protection, Inc., Dr. James Zeigler at DuPont Personal Protection, and Dr. Claudiu Lungu at University of Alabama at Birmingham for helpful discussions; and NIOSH colleagues including Drs. Mark Hoover, Ralph Zumwalde, and Li-Ming Lo for their review comments on the manuscript.

Mention of any commercial product or trade name does not constitute endorsement by the National Institute for Occupational Safety and Health (NIOSH). The findings and conclusions of this report are those of the author(s) and do not necessarily represent the views of NIOSH.

Notes

^ABoth Fabric F and G are composed of three layers, and fibers in the middle layer are much finer than those in the outer layers. Hence, the middle layer was considered the main layer and its physical properties were presented.