MSGID: 1:317/3 6272018d   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Face shape influences mask fit, suggests problems with double masking   
   against COVID-19    
    Proper fit crucial for optimal mask protection    
      
     Date:   
         May 3, 2022   
     Source:   
         American Institute of Physics   
     Summary:   
         In a new study, researchers used principal component analysis along   
         with fluid dynamics simulation models to show the crucial importance   
         of proper fit for all types of masks and how face shape influences   
         the most ideal fit. They modeled a moderate cough jet from a mouth   
         of an adult male wearing a cloth mask over the nose and mouth with   
         elastic bands wrapped around the ears and calculated the maximum   
         volume flow rates through the front of mask and peripheral gaps   
         at different material porosity levels.   
      
      
      
   FULL STORY   
   ==========================================================================   
   In its updated guidance at the start of 2022, the U.S. Centers for   
   Disease Control and Prevention said loosely woven cloth masks offer   
   the least protection against COVID-19, and N95 and KN95 masks offer the   
   most protection.   
      
   Still, after more than two years since the pandemic began, there is   
   not a full understanding of mask characteristics for the most optimal   
   protection.   
      
      
   ==========================================================================   
   In Physics of Fluids, published by AIP Publishing, researchers at Florida   
   State University and Johns Hopkins University use principal component   
   analysis (PCA) along with fluid dynamics simulation models to show the   
   crucial importance of proper fit for all types of masks and how face   
   shape influences the most ideal fit.   
      
   The study suggests double masking with improperly fitted masks may   
   not significantly improve mask efficiency and produces a false sense   
   of security.   
      
   More layers mean a less porous face covering, leading to more flow forced   
   out of the perimeter gaps (sides, top, and bottom) in masks with a less   
   secure fit.   
      
   Double layers increase filtering efficiency only with good mask fit but   
   could also lead to breathing difficulties.   
      
   The researchers modeled a moderate cough jet from a mouth of an adult male   
   wearing a cloth mask over the nose and mouth with elastic bands wrapped   
   around the ears. They calculated the maximum volume flow rates through the   
   front of mask and peripheral gaps at different material porosity levels.   
      
   For a more realistic 3D face shape and size, the researchers used PCA   
   that integrated 100 adult male and 100 adult female heads retrieved from   
   head scan data at Basel University in Switzerland. PCA condenses large   
   sets of variables while retaining most of information.   
      
   Their model showed how the slight asymmetry typical in all facial   
   structures can affect proper mask fitting. For example, a mask can have   
   a tighter fit on the left side of the face than on the right side.   
      
   "Facial asymmetry is almost imperceivable to the eye but is made obvious   
   by the cough flow through the mask," said co-author Tomas Solano, from   
   Florida State University. "For this particular case, the only unfiltered   
   leakage observed is through the top. However, for different face shapes,   
   leakage through the bottom and sides of the mask is also possible."   
   Creating "designer masks" customized to each person's face is not   
   practical at scale. Still, PCA-based simulations can be used to design   
   better masks for different populations by revealing general differences   
   between male and female or child versus elderly facial structures and   
   the associated air flow through masks.   
      
      
   ==========================================================================   
   Story Source: Materials provided by American_Institute_of_Physics. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Tomas Solano, Chuanxin Ni, Rajat Mittal, Kourosh Shoele. Perimeter   
         leakage of face masks and its effect on the mask's efficacy. Physics   
         of Fluids, 2022; 34 (5): 051902 DOI: 10.1063/5.0086320   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220503110525.htm   
      
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