With the Centers for Disease Control and Prevention’s new guidelines around face masks out, many people have been wondering about how to use them effectively.
Last week, the California Department of Health also released guidelines regarding face coverings, stating that used in conjunction with social distancing, cloth masks could be a good way to reduce asymptomatic spread by blocking respiratory droplets. Our listeners wanted a little more detail on these guidelines though. Here are some of the questions they had.
What are the recommendations around cloth masks versus surgical masks?
The general hierarchy of effectiveness in blocking viral particles tends to rank cloth masks as the least effective, surgical masks second as they block 65 percent of particles, and then N95 masks which block about 95 percent of particles. But the CDC has recommended that civilians who aren't front-line workers like nurses and other first responders use cotton masks when going out in public.
Recently, researchers at Wake Forest University in North Carolina tested the effectiveness of cloth masks and found the results were extremely variable depending on the construction and type of material that was used.
Scott Segal, professor and Chair of Anesthesiology at Wake Forest School of Medicine, led the research.
“Cloth masks were all over the place. We had some that outperformed surgical masks, our best was [blocking] 77 to 79 percent, but we also had some that were lower and we had one that only filtered 1 percent,” he said. “So we felt it was important to try to guide consumers in selecting materials in what made the best masks.”
According to Segal, the most effective cotton mask is one made from a thicker, more tightly woven fabric, such as batik or quilter’s cotton, which had a thread count of 180 or more. They found that double-layered masks performed better than single-layered ones, and that even masks made from thick cotton t-shirts could be moderately effective. For those unable to find thick cotton, a thin cotton layer over a flannel layer also seemed to work well.
“In trying to assess a piece of fabric in your house, what we found to be the best rule of thumb was to simply hold up the fabric to a bright light or to the sun, and see if you can see the light shining through the fabric outlining the individual fibers,” Segal said.
He also noted a tie-on design for those making masks for donation was preferable, as those are more adjustable than elastic ear loops.
How do I clean my cloth mask? And how often should I do this?
Experts say regularly laundering a mask with any type of detergent and then running it through the heat of the dryer should be enough to disinfect it. They also recommend washing masks every day or two, and letting masks dry in between wearings. Segal said he has not yet looked into the effect that multiple washes or washes with bleach can have on the mask, so laundering them is about finding a balance between destroying the mask’s construction and keeping it clean.
“We have advised washing the mask in a regular machine cycle. We believe that the heat and detergent in the washing machine and the dry heat in the dryer will probably do a good job of disinfecting the mask,” he said.
Do you need to sanitize masks before donating them?
Unused cloth masks can be donated without being washed first. Some hospitals have actually started washing all donated cloth masks before they’re used anyways. Segal said he’s heard that pre-washing fabric can actually tighten the fibers in cloth and make them more effective, so those considering donations can pre-wash if they’re interested but it isn’t necessary. Donating used surgical masks or N95 masks is not a good idea.
He said many healthcare facilities were using homemade masks donations sparingly at this point and that frontline workers were still using commercially-made masks.
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