Author ORCID Identifier

https://orcid.org/0000-0002-2849-2786

Semester

Summer

Date of Graduation

2023

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Industrial and Managements Systems Engineering

Committee Chair

Warren R. Myers

Committee Member

Ashish Nimbarte

Committee Member

Jeremy Gouzd

Committee Member

Zhichao Liu

Committee Member

Kenneth J. Ryan

Committee Member

Ziqing Zhuang

Abstract

This study aimed to assess the effectiveness of different types of respiratory protection, including National Institute for Occupational Safety and Health (NIOSH) Approved respirators and surgical masks in healthcare settings, as well as barrier face coverings (BFCs) used by the public as source control. The assessment was based on three components: total outward leakage (TOL), particle size distribution, and exhalation airflow velocity. To achieve this, the study utilized headform testing systems to measure TOL and airflow velocity. Specifically, a hard surface headform was used for NIOSH Approved respirators and surgical masks, while two soft surface headforms of different sizes were used for the BFCs used by the public. The findings revealed that N95 filtering facepiece respirators (N95 FFRs) were more effective in reducing outward leakage compared to surgical masks (SMs), but proper fit was crucial for both. Elastomeric half-mask respirators (EHMRs) and N95 FFRs with an exhalation valve (N95 FFRVs) were not suitable for source control in healthcare settings, especially during high flowrate activities. The effectiveness of ASTM medical masks in reducing outward leakage was comparable to surgical masks while that of ASTM Level 3 masks was compromised by poor fit. The single-layer cloth BFCs were ineffective, while the multiple-layer cloth masks equipped with HEPA or PM 2.5 filters had better performance. The size of the headform is a crucial factor that significantly impacts the TOL. On average, when BFCs are worn on a medium-sized headform, they exhibit a higher TOL compared to those worn on a large-sized headform. The study also highlighted the limitations of NIOSH approved respirators against certain particle sizes, which are more likely to spread infectious viruses via airborne transmission. Both medical and nonmedical BFCs were effective in reducing exhalation airflow velocity but had limitations in source control against certain particle sizes. The study emphasized the importance of proper fit testing, adequate training, and adherence to protocols for optimal respiratory protection. Additionally, it is imperative to practice ventilation and social distancing even though a source control measure is implemented.

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