Face shield intensifies inhaled exposure to self-generated bio-effluents

• Published in: Building and environment Vol. 217; p. 109070
• Main Authors: Jia, Zhongjian, Ai, Zhengtao
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2022; Elsevier BV
• Subjects: Boundary conditions; CFD simulation; Computational fluid dynamics; Computer applications; Dilution; Effluents; Exhalation; Exposure; Face; Face shield; Federal regulation; Flow characteristics; Fluid dynamics; Hydrodynamics; Mathematical models; Negative effect; Nose; Personal protective equipment; Pollutants; Protective clothing; Respiration; Self-generated bio-effluents; Skin; Ventilation; Self-generated bio-effluents; CFD simulation; Personal protective equipment; Exposure; Face shield; Negative effect
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2022.109070

The presence of a face shield may block the forward and upward dilution of bio-effluents, generated from one's own exhalations and skin, through the breathing zone, which might thus intensify the user's inhaled exposure, especially for long-term use. The objective of this study is to quantify this exposure risk. The flow characteristics of the porous region at the top of a typical face shield were tested experimentally. The viscous resistance coefficient and inertial resistance coefficient of the porous region were 4.9 × 107 and −402, respectively. The influence of breathing mode (via mouth and nose), pulmonary ventilation rate (6–8 L/min), and bio-effluents generation location (i.e., exhalation, groin, and armpit) on the exposure risk of bio-effluents were then studied by computational fluid dynamics (CFD) technology in combination with the species transport model. The inhaled fraction (iF) index was used to assess the exposure risk. A face shield can considerably increase the exposure risk, the inhaled fraction index being increased from 0.28% to 2.97% for skin pollutants, and from 2.25% to 6.96% for exhaled pollutants. It means that the fraction of oxygen (O2) in the inhaled air of face shield wearers is 20.58%, being 2% less than that without face shield. For face shield wearers, a higher pulmonary ventilation rate and breathing through nose would further increase the exposure risk. This information would be important boundary conditions for accurate simulation and design of face shield as well as the design of protective clothing. [Display omitted] •Inhaled fraction index (iF) is reliable index for evaluating bio-effluents exposure.•Face shield leads to an increase of iF from 0.28% to 2.97% for skin bio-effluents.•Face shield leads to an increase of iF from 2.25% to 6.96% for exhaled bio-effluents.•Face shield leads to a decrease of the fraction of oxygen in inhaled air by 2%.•Pulmonary ventilation rate rises from 6 to 8 L/min leading to a 26.6% increase of iF.