Evaluation of Flow Rate and Leakage on Mask Effectiveness and Investigation of Double Masks

Citation

Chea, Peter Hing-Yin (2022) Evaluation of Flow Rate and Leakage on Mask Effectiveness and Investigation of Double Masks. Senior thesis (Major), California Institute of Technology. doi:10.7907/jrw9-h427. https://resolver.caltech.edu/CaltechTHESIS:07252024-034444812

Abstract

Mask-wearing emerged as the primary safety measure to prevent spreading COVID-19. During the COVID-19 pandemic, there was growing evidence that SARS-CoV-2 could spread by aerosol transmission. Thus, increased understanding of mask performance was important to help reduce viral transmission. In addition, the CDC recommended wearing double masks to provide better fit and additional protection when people could not access respirators. This thesis aims to investigate the performance of single mask and double mask combinations, and using a parallel resistance model to quantify leakage.

Multiple copies of different mask types were tested: N95 respirators, KN95 respirators, procedure masks, and cloth masks. For all of the single masks, the penetration increased with flow rate, while the most penetrating particle size (MPPS) generally decreased. The peak penetration is lowest for N95 respirators, and the peak penetration is highest for cloth masks at all flow rates. For double masking, we observe that wearing a combination of cloth and procedure masks has a higher amount of decreased penetration and a lower amount of increased pressure drop than a combination involving N95 and KN95 respirators. For quantifying leakage, a parallel resistance model was used to calculate the resistance for leaks. The procedure and cloth masks had lower resistance for leaks and leakage flow rates than N95 and KN95 respirators. The procedure and cloth masks are more susceptible to leaks than respirators and thus reducing the effectiveness of these masks.

Thesis Files