- 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.
Throughout the COVID-19 pandemic, face masks have continued to play an important role in helping to minimize the spread of the disease. To date, some cities, counties, states, and countries still have mask mandates in place, requiring face masks in certain buildings or situations.
The CDC recommends using face masks that:
- have two or more layers of fabric that is breathable and washable
- cover the nose and mouth of the wearer completely
- fit snugly along the sides of the face with no gaps
- use a nose wire to keep the mask closed at the top
Over the past year, research has emerged regarding the effectiveness of using a face mask to safeguard a person from the coronavirus. One study provided evidence that surgical face masks help prevent transmission of COVID-19 from one person to another. Another study says face masks may help lessen the severity of COVID-19 because they increase breathing air humidity levels.
Research has also looked at the effectiveness of various medical- and consumer-grade masks.
In this new study, lead author Francoise Blachere, MSc, a research biologist with the NIOSH, and her team believe certain face mask combinations — such as double masking — and fit modifications provide greater defense against the SARS-CoV-2 virus.
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.
Another breathing simulator evaluated the number of aerosol particles that escaped from the different tested face masks, both with fit modifications and without, during simulated breathing and coughs.
Through their research, Blachere and her team found double masking with a three-ply cloth mask or a medical mask provided the best protection against respiratory aerosols. Medical masks without any type of modification blocked around 42% of exhaled aerosols and around 56% of cough aerosols.
However, when using cloth and medical masks in tandem, the combination stopped around 91% of exhaled aerosols and around 85% of cough aerosols.
When factoring in fit modifications, the researchers found a brace placed over the medical mask resulted in blocking around 99% of exhaled aerosols and 95% of cough aerosols. Researchers found both mask brace and earloop toggle modifications helped improve the fit of medical masks, creating a better seal between the edges of the mask and the wearer’s face. The mask brace also improved the fit of cloth masks.
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.
“It just highlights the importance [of] paying attention — it’s not just wearing a mask, but how the mask fits. And taking these little steps to make sure you’re optimizing your own protection, whether it’s by adding a brace or tie behind the ears.”
– Dr. Youssef
Blachere said future studies will examine how well different mask designs and materials work. Researchers will also study how different breathing rates and cough volumes affect the performance of the mask.
“We also hope to develop a model that can predict how well the mask blocks coughed and exhaled aerosols using widely-used standard tests of filtration performance and fit,” Blachere added.
Dr. Youssef would like to see further research conducted on how often reusable masks need replacing. Research like this can help provide more guidance to everyday face wearers to help them assess the fit of their face masks.
“In healthcare, we do mask fit testing to make sure that the masks that we’re wearing […] are fitting us perfectly,” Dr. Youssef explained. But ideally, there would be “some rudimentary tool that ordinary people at home can put on their mask and say okay, this is a good fit, or I need to do something to optimize it.”
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