Analytical and numerical investigation of the airflow in face masks used for protection against COVID-19 virus -- implications for mask design and usage

TL;DR

This study combines analytical and numerical methods to analyze airflow leakage in face masks, revealing that small gaps significantly compromise mask effectiveness and suggesting design improvements for better protection.

Contribution

It provides a comprehensive fluid dynamics analysis of mask leakage, demonstrating the impact of gap size on protection standards and proposing design enhancements.

Findings

Gaps larger than 0.1mm reduce mask efficacy below standards

Most airflow and droplets pass through 1mm gaps

Simplified models effectively predict airflow behavior

Abstract

The use of face masks for the general public has been suggested in literature as a means to decrease virus transmission during the global COVID-19 pandemic. However, literature findings indicate that most mask designs do not provide reliable protection. This paper investigates the hypothesis that the impaired protection is mainly due to imperfect fitting of the masks, so that airflow, which contains virus-transporting droplets, can leak through gaps into or out of the mask. The fluid dynamics of face masks are investigated via analytical and numerical computations. The results demonstrate that the flow can be satisfactorily predicted by simplified analytical 1D-flow models, by efficient 2D-flow simulations and by 3D-flow simulations. The present results show that already gap heights larger than 0.1mm can result in the mask not fulfilling FFP2 or FFP3 standards, and for gap heights of ca. 1mm most of the airflow and droplets may pass through the gap. The implications of these findings are discussed and improvements to existing mask designs are suggested.