Physics of How Masks Affect Airflow and COVID-19 Protection

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Pressure and Particle Motions Mask

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Pressure and particle movements with and without a mask. Credit: Jinxiang Xi

A computer system design deepens our understanding of air flow while using face masks, where particles land in the breathing system and the efficiency of three-layer surgical masks.

Even though it has actually been commonly understood that using a face mask will assist alleviate the neighborhood spread of COVID-19, less is understood relating to the particular efficiency of masks in minimizing the viral load in the breathing systems of those using them.

In Physics of Fluids, by AIP Publishing, scientists from the University of Massachusetts Lowell and California Baptist University analyzed the impact of using a three-layer surgical mask on inspiratory air flows and the mask’s results on the inhalation and deposition of ambient particles in the upper breathing air passages.

“It is natural to think that wearing a mask, no matter new or old, should always be better than nothing. Our results show that this belief is only true for particles larger than 5 micrometers, but not for fine particles smaller than 2.5 micrometers,” stated author Jinxiang Xi. (The SARS-CoV-2 infection that triggers COVID-19 has to do with 0.1 micrometers. — ed.)

The scientists discovered that using a mask with low (less than 30%) purification performance can be even worse than without.

They established a computational face mask design utilizing a physiologically reasonable design of an individual using a surgical mask with pleats and after that utilizing mathematical approaches to track the particles through the mask. They analyzed the habits and fates of aerosols going through the mask, onto the face, into the respiratory tract, and, ultimately, where they transfer in the nose, vocal cords, or deep lung.

The design revealed a mask alters the air flow around the face, so that rather of air going into the mouth and nose through particular courses, air gets in the mouth and nose through the whole mask surface area however at lower speeds.

The lower speed near the face prefers the inhalation of aerosols into the nose, so despite the fact that masks filter out specific varieties of particles, more particles getting away mask purification can go into the breathing system.

They discovered the purification performance of the three-layer surgical mask can differ from 65%, if brand-new, to 25%, when utilized, so using a 65% mask appropriately will offer great defense, however using a 25% purification mask can be even worse than not using one at all.

“We hope public health authorities strengthen the current preventative measures to curb COVID-19 transmission, like choosing a more effective mask, wearing it properly for the highest protection, and avoid using an excessively used or expired surgical mask,” stated Xi.

The scientists discovered the pleats of a surgical face mask considerably impact air flow patterns, recommending that mask shape ought to likewise be thought about as a crucial element when approximating mask defense performance and creating brand-new masks. Xi stated they will even more study the results of mask shapes on human respiratory tract defense performance.

Reference: “Effects of mask-wearing on the inhalability and deposition of airborne SARS-CoV-2 aerosols in human upper airway” by Jinxiang Xi, Xiuhua April Si and Ramaswamy Nagarajan, 15 December 2020, Physics of Fluids.
DOI: 10.1063/5.0034580



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