Influence of face shields on exposures to respirable aerosol

Abstract

The objective of this study was to determine the influence of face shields on the concentration of respirable aerosols in the breathing zone of the wearer. The experimental approach involved the generation of poly-dispersed respirable test dust aerosol in a low-speed wind tunnel over 15 min, with a downstream breathing mannequin. Aerosol concentrations were measured in the breathing zone of the mannequin and at an upstream location using two laser spectrophotometers that measured particle number concentration over the range 0.25–31 µm. Three face shield designs were tested (A, B, and C) and were positioned on the mannequin operated at a high and low breathing rate. Efficiency—the reduction in aerosol concentration in the breathing zone—was calculated as a function of particle size and overall, for each face shield. Face shield A, a bucket hat with flexible shield, had the highest efficiency, approximately 95%, while more traditional face shield designs had efficiency 53–78%, depending on face shield and breathing rate. Efficiency varied by particle size, but the pattern differed among face shield designs. Face shields decreased the concentration of respirable aerosols in the breathing zone when aerosols were carried perpendicular to the face. Additional research is needed to understand the impact of face shield position relative to the source.

Keywords:

• Infectious diseases
• personal protective equipment
• wind tunnel

Data availability statement

The data that support the findings of this study are openly available in The Hive: University of Utah Research Data Repository at https://doi.org/10.7278/S50d-be9d-yp2c

Additional information

Funding

This research was supported by the University of Utah Office of the Vice President for Research in partnership with the Immunology, Inflammation and Infectious Disease (3i) Initiative. MW received additional financial support from the Rocky Mountain Center for Occupational and Environmental Health, CDC/NIOSH T42/OH008414.