The research study recommends double masking with improperly fitted masks may not substantially improve mask effectiveness and produces an incorrect sense of security.
Time advancement of cough while wearing a face mask. Credit: Tomas Solano
More layers suggest a less permeable face covering, leading to more flow displaced of the perimeter gaps (sides, leading, and bottom) in masks with a less safe and secure fit. Double layers increase filtering effectiveness only with excellent mask fit however could also cause breathing difficulties.
The scientists designed a moderate cough jet from a mouth of an adult male wearing a cloth mask over the nose and mouth with rubber bands wrapped around the ears. They calculated the maximum volume flow rates through the front of mask and peripheral gaps at various product porosity levels.
For a more practical 3D face sizes and shape, the researchers utilized PCA that incorporated 100 adult male and 100 adult female heads obtained from head scan information at Basel University in Switzerland. PCA condenses big sets of variables while retaining most of the info.
Their model demonstrated how the small asymmetry typical in all facial structures can affect appropriate mask fitting. A mask can have a tighter fit on the left side of the face than on the ideal side.
” Facial asymmetry is practically imperceivable to the eye however is made obvious by the cough circulation through the mask,” stated co-author Tomas Solano, from Florida State University. “For this particular case, the only unfiltered leakage observed is through the top. For different face shapes, leakage through the bottom and sides of the mask is likewise possible.”.
Developing “designer masks” personalized to each persons face is not practical at scale. Still, PCA-based simulations can be used to develop much better masks for various populations by exposing general distinctions in between male and female or kid versus elderly facial structures and the associated airflow through masks.
Recommendation: “Perimeter leak of face masks and its effect on the masks efficacy” by Tomas Solano, Chuanxin Ni, Rajat Mittal and Kourosh Shoele, 3 May 2022, Physics of Fluids.DOI: 10.1063/ 5.0086320.
Time evolution of cough while wearing a face mask. Credit: Tomas Solano
Correct Fit Crucial for Optimal Mask Protection
Face shape influences mask fit, suggests problems with double masking versus COVID-19.
In its updated guidance at the start of 2022, the U.S. Centers for Disease Control and Prevention (CDC) said loosely woven fabric masks offer the least security against COVID-19, and N95 and KN95 masks provide the most security. Still, after more than 2 years since the pandemic began, there is not a complete understanding of mask characteristics for the most optimum security.
In Physics of Fluids, published by AIP Publishing, scientists at Florida State University and Johns Hopkins University usage principal element analysis (PCA) together with fluid dynamics simulation models to reveal the important significance of appropriate fit for all types of masks and how face shape affects the most ideal fit.
