Wearing two face coverings can nearly double the filtering efficiency of the masks against particles the size of the novel coronavirus and reduces the chances of wearers contracting Covid-19, according to a new study.
While medical masks are designed to have good filtration potential owing to the materials used to make them, their fit is not always perfect for everyone, researchers from the University of North Carolina (UNC), noted.
The study, published in the journal JAMA Internal Medicine, found that double masking enhanced filtration, not so much due to the addition of cloth layers, but by eliminating gaps and poor-fitting areas of masks.
“With the current data supporting how effective mask-wearing is at preventing the spread of Covid-19, the best kind of double-masking is when you and the person you are interacting with are each correctly wearing a very snug-fitting mask,” said Emily Sickbert-Bennett, lead author of the study.
In the research, the team filled a 10-ft by 10-ft stainless-steel exposure chamber with small salt particle aerosols, and had scientists wear combinations of masks.
They tested how effective the combinations were at keeping particles out of their breathing space.
A probe attached to the masks measured the concentration of particles entering the breathing space underneath the researcher’s face coverings.
“We also had the researchers in the chamber undergo a series of range-of-motion activities to simulate the typical motions a person may do throughout their day – bending at the waist, talking, and looking left, right, up and down,” said Phillip Clapp, co-author of the study from UNC.
According to the report, enhancements that improve the seal between the mask and the facial skin dramatically improve the filtration efficiency of the face masks.
“Results of this quality improvement study demonstrated that wearing a medical procedure mask underneath a cloth mask provided the best improvement to FFE [fitted filtration efficiency] of all the combinations evaluated,” the scientists said.
Citing the limitations of the study, the researchers said they tested only one type of medical procedure mask, and that only three volunteers participated in the mask evaluations.