Health Matters spoke with Dr. Simon, an assistant professor of medicine in the Division of Infectious Diseases at Weill Cornell Medicine, to understand the different kinds of masks and why it might make sense to start double masking.
Is double masking a good idea?
Dr. Simon: Let’s start off with one key point, and that is: Any mask or face covering is better than no mask or face covering. Data has proved that. In terms of double masking, the CDC now lists it as one way to improve protection from the virus, and some leaders, such as Dr. Anthony Fauci, the nation’s top infectious disease expert, have said they often double mask. If worn correctly, two masks can improve mask fit and serve as an additional barrier to filter infectious particles. Recent laboratory-based experiments performed on dummies have shown that exposure to potentially infectious small particles (aerosols) decreased by about 96% when both dummies were double masked.
Also, it’s important to remember that just because someone is wearing two masks, they should not forget about all the other important behaviors to prevent transmission, like social distancing, avoiding crowded indoor environments when possible, and hand hygiene.
What makes a face mask high-quality?
The two most important characteristics that people should look for in a good, high-quality face mask are the fit and filtration. The fit prevents air from leaking around the edges of the mask, and the filtration blocks potentially infectious respiratory droplets. If it’s a cloth mask, it should be made of tightly woven fabric, like cotton or a cotton blend, with a high thread count, and have at least two layers. This allows the mask to effectively block or filter infectious particles. The mask should fit snugly so that it covers the face and mouth and extends below the chin. Ideally, it should be breathable and comfortable too, because you have to be able to wear it and not worry about readjusting or taking it off and putting it back on.
A few options that the CDC now recommends to improve mask fit include wearing a mask with a nose wire, using a mask fitter or brace, or, for disposable masks, knotting and tucking the ear loops at the edge of the mask. This knotting and tucking method was also evaluated in the recent study with laboratory dummies and also found to be highly effective at reducing exposure to potentially infectious aerosols. One way to check the fit of the mask is to cup your hands around the outside edges of the mask and breathe in/out several times, checking to see if air leaks out the sides or near your eyes.
What about medical-grade masks, like ASTM Level 3 and KN95 masks?
ASTM Level 3 masks are considered medical-grade masks and — like the N95 respirator masks — they should still be reserved for healthcare workers. KN95 masks, which are available for public use, have a similar design to N95 masks and may have a high level of protection. However, there have been issues with counterfeit and quality standards. The Food and Drug Administration lists certain KN95s that have been evaluated and passed quality standards, which is worth taking a look at before purchasing.
What are some ways to double mask or improve the filtration of a cloth mask?
The recommended way to double mask is to wear a disposable mask underneath with a cloth face mask fitted on top of it. This technique allows the disposable mask to act as a filter, and the cloth mask provides an additional layer of filtration while improving the fit of the disposable mask.
Another recommended option is to wear a three-layer mask: A cloth mask made of a flexible, tightly woven fabric with a nonwoven high-efficiency filter material sandwiched between them the two cloth layers. Researchers suggest that a filter that’s akin to a vacuum bag filter, or nonwoven polypropylene, is highly effective at filtering small particles that are the size we worry about with COVID-19. A lot of the cloth masks have pockets where you can insert a filter. So a well-fitted cloth face mask with an added filter is thought to be equivalent to double masking.
Importantly, it is not recommended to wear two disposable masks on top of each other.