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Not all masks are effective against COVID-19: Here’s a ranking of how safe they are

mask safety coronavirus
Photo via Emma Fischer/Duke University

When it comes to face-covering offerings, there is no shortage of options during the COVID-19 pandemic, as mask safety has become paramount to help to protect others from the coronavirus. 

At the beginning of the pandemic, when hospitals ran out of N95 and surgical masks because of public hoarding, many people around the world began to make DIY masks. Now, there’s a vast and diverse market of face-covering businesses.  

With so many options to choose from, it’s essential to know what materials work best. After all, it’s not just about looking cute—your mask needs to be effective, too (after all, procuring the best face mask you can find is key). 

Thanks to researchers at Duke University, people now have a better idea of what mask materials are the most protective.

In a new study published on Aug. 7, the researchers released the results from testing 14 commonly available masks or mask alternatives, one patch of mask material, and a professionally fit-tested N95 mask to see how effective they were at “suppress[ing] the spread of respiratory droplets during regular speech.” 

The researcher’s experiment was relatively inexpensive and straightforward, according to the study. To measure the respiratory droplets, the researchers had someone wear a face mask and speak into an expanded laser beam inside a dark enclosure. 

“Droplets that propagate through the laser beam scatter light, which is recorded with a cell phone camera,” the study explained. “A simple computer algorithm is used to count the droplets in the video.”

The experiment found that the most protective masks were the fitted N95, the surgical mask, the poly/cotton mask, the polyprop mask, and the swath mask. 

The least effective masks were the knitted mask, the bandana, and the fleece mask. The fleece mask, also called a neck gaiter, was actually less effective than not wearing a mask at all, according to the study. 

“We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets, which explains the apparent increase in droplet count relative to no mask in that case,” the study says. “Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive.” 

Neck gaiters aren’t helpful for mask safety

Neck gaiters have become a popular option for runners because their spandex material makes them more breathable. Warren S. Warren, one of the study’s co-authors, told the Washington Post that its convenience is also what it makes it ineffective. 

“These neck gaiters are extremely common in a lot of places because they’re very convenient to wear,” he said. “But the exact reason why they’re so convenient, which is that they don’t restrict air, is the reason why they’re not doing much of a job helping people.”

But science journalist Cynthia McKelvey noted that more definitive data is needed. As she tweeted, “They were only testing THE METHOD OF MEASURING DROPLETS. It provides some interesting but NOT EXHAUSTIVE MEASURES THE EFFECTIVENESS OF DIFFERENT TYPES OF MASKS. Should you wear a mask? YES! THE DATA ARE CLEAR THAT MASKS ARE HELPFUL. Should you consider a more fitted one over a gaiter? Probably! But we just NEED MORE DATA ON ALL MASKS.”

In a press release, Duke University physician Dr. Eric Westman said this study proved that thinking about mask safety and wearing the right covering is an easy way to reduce the spread of COVID-19. 

“If everyone wore a mask, we could stop up to 99% of these droplets before they reach someone else,” Westman said. “In the absence of a vaccine or antiviral medicine, it’s the one proven way to protect others as well as yourself.”

Here is the complete ranking of masks in the study, from most protective to least: 

  1. Fitted N95 
  2. Surgical 
  3. Poly/Cotton 
  4. PolyProp
  5. Swath 
  6. Cotton5
  7. Cotton2 
  8. Valved N95
  9. Cotton4 
  10. MaxAT
  11. Cotton1
  12. Cotton3 
  13. Knitted 
  14. Bandana 
  15. None
  16. Fleece 

Read the study to see photos of each face-covering. 

Read more on coronavirus face coverings:

Sources: AAAS, Washington Post, Duke University


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