US health authorities already recommend people wear N95 and KN95 masks, as they offer the most protection against the disease, while loosely woven cloth masks have been found to offer the least protection.
But researchers at Florida State University (FSU) said there is still not a full understanding of mask characteristics for the most optimal protection, over two years since the pandemic began.
They used a technique called principal component analysis (PCA) along with fluid dynamics simulation models to show the importance of proper fit for all types of masks and how face shape influences the ideal fit.
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. While double layers do increase the filtering efficiency, they only do so with a good mask, the researchers said. The downside is that a tight fit can also lead to breathing difficulties.
The researchers...