Face masks and COVID-19

Face masks have been widely used throughout the COVID-19 pandemic to protect people from catching the virus.

Researchers discovered certain double masking combinations and fit modifications offer increased protection from respiratory diseases.

The research team says that as well as the materials a face mask is made of, how well it fits can determine its efficiency.

A research team from the National Institute for Occupational Safety and Health (NIOSH), part of the Centers for Disease Control and Prevention (CDC), says certain face mask combinations and fit modifications offer greater protection from diseases that spread through respiratory droplets, such as COVID-19.

The scientists believe their research — conducted on both human and simulator manikin subjects — can help offer greater protection for healthcare workers, hospital patients, and the public from respiratory infectious diseases like COVID-19.

The results from this study appear in the journal American Journal of Infection Control, the journal of the Association for Professionals in Infection Control and Epidemiology.

Evaluating mask types and fits

For the study, researchers used two types of medical masks and three types of cloth masks purchased online. The medical masks included a three-ply disposable protective mask and a three-ply disposable surgical mask. Both medical masks included elastic ear loops and adjustable metal nose strips.

The cloth masks included a two-ply polyester blend with earloops, a three-ply 100% cotton mask with earloops and adjustable metal nose strip, and a four-ply polyester blend face mask with earloops and adjustable metal nose strip.

Researchers also evaluated a variety of mask fit modification devices purchased online. These included plastic mask brackets worn under a face mask, earloop straps and toggles, and a brace worn over a mask. The researchers also used earloop modifications such as crossing the ear loops to create a loop that fits over the wearer’s ear. Another modification included knotting earloops for a snugger fit around the ears and tucking the excess loop material under the knot.

Scientists used a combination of human subjects and simulators using manikins to conduct their research. The research involved the number of aerosol particles — microscopic particles suspended in the air from when you breathe, cough, or sneeze — that a mask allows to escape.

The research team used a source control measurement system to measure the percentage of aerosol particles blocked by both fit-modified and unmodified face masks.

The importance of filtering and fit

When deciding what types of face masks to use, Blachere and her team believe it is important for healthcare workers and the general public to take into consideration the filtering properties of the materials used in the construction of a face mask, as well as the fit of the mask.

“Respiratory droplets and aerosols are expelled in a broad range of particle sizes,” Blachere told MNT. “Our research shows that to be effective as a source control device, a face mask must be a good filter, but it also must fit well. Moving forward, it is important that the filtering properties of the materials used in the construction of a face mask are taken into consideration. Likewise, the design of the face mask should ensure a snug fit without any gaps or face seal leaks.”

Dr. Fady Youssef, a board certified pulmonologist, internist, and critical care specialist at MemorialCare Long Beach Medical Center in Long Beach, CA, also spoke with MNT. He hopes new research like this leads to new face mask options offering even greater protection against aerosol particles.

“The modifications offered significant step ups in [the] protection that the masks at baseline offered,” Dr. Youssef explained.