Double masking or knotting and tucking a single medical procedure mask helps prevent air leakage and improve mask performance, according to the CDC's Feb. 10 Morbidity and Mortality Weekly Report.
After performing lab experiments with dummies, the CDC found that modifying masks to tighten the fit reduced exposure to potentially infectious aerosols, including those in the size range able to transmit SARS-CoV-2, by about 95 percent.
Researchers evaluated two modifications: Layering a cloth mask over a medical procedure mask, known as double masking, and a single medical procedure mask with knotted ear loops and tucked-in sides to help get rid of any loose material. When the infected wearer (source) and receiver were both fitted with the double mask or knotted and tucked mask modifications, the cumulative exposure of the receiver was reduced by 96.4 percent and 95.9 percent for each modification, respectively.
The report also highlighted the use of solid or elastic mask fitters and a modification where a nylon cover is placed over a mask, as additional effective options to improve mask fit.
"The data in this report underscore the finding that good fit can increase overall mask efficiency," the CDC said. "Multiple simple ways to improve fit have been demonstrated to be effective."
To view the full report, click here.