N95s offer the best protection against coronavirus, but neck membranes can multiply infectious particles
We’ve all been told to wear face masks to reduce the spread of the coronavirus, but it turns out that the material your mask is made of can affect your risk, a new study suggests.
An N95 mask, which filters almost all small and large particles, most reduced the risk of contracting COVID-19, the disease caused by the virus.
But some masks were actually worse than not wearing a mask at all, because they turned large potentially infected droplets into smaller droplets than can linger in the air for longer.
The team, from Duke University, says the findings prove that not all face masks are created equal and can advise Americans on what to wear and what not to wear when going out in public.
Researchers tested 14 different types of masks and found that N95s (# 14) were the best, followed by three-layer surgical masks (# 1) and different cotton masks (# 4-10 and # 13)
For the study, published in the journal Science Advancesthe team examined 14 different types of facial covers.
Researchers cut a hole for a black box for a speaker to talk to and covered it with a thin sheet of light from a laser beam.
Then they placed a cell phone camera in the back and recorded the breath droplets cutting through the laser beam as they talk.
One person spoke to the hole and said the phrase “Stay healthy, folks,” wearing the different types of coverings.
1. Three layer surgical mask
2. N95 mask with exhalation valve
3. Knitted mask
4. Two-layer apron mask made of polypropylene
5. Cotton-polypropylene-cotton mask
6. Single layer Maxima AT mask
7. Cotton mask with two layers, pleated
8. Two-layer cotton mask, Olson style
9. Cotton mask with two layers, pleated
10. Single layer cotton pleated style mask
11. Gaiter type neck fleece
12. Double layer bandanna
13. Cotton mask with two layers, pleated
14. N95 mask, no exhalation valve, fitted
The results showed that N95 masks, which are designed to prevent 95 percent of the particles from getting in or out, were the most effective.
Knitted masks and bandanas provided excellent protection against litter while wearing a neck fleece was worse than no mask as it turned large drops into smaller drops (above)
Three-layer surgical masks and homemade cotton masks, which people made at home, also prevented particles from coming out.
Cotton face covers “provided good coverage, eliminating a significant amount of the spray from normal speech,” the researchers wrote.
Among the worst performing, however, were folded bandanas and knitted masks, which may look fashionable but barely prevent particles from entering.
In fact, there was one type of mask that was actually worse than not wearing a face cover at all.
Neck pads, also called leggings – often worn by runners – increased the number of respiratory drops by turning large drops into smaller drops.
Because smaller droplets stay in the air longer than larger droplets, the mask can trap those particles, and neck membranes are in fact ‘counterproductive’.
“ We were extremely surprised to find that the number of particles measured with the fleece was actually greater than the number of particles measured without wearing a mask, ” said study co-author Dr. Martin Fischer, an associate professor in the chemistry department. CNN.
“We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”
The team says people should continue to wear masks, but added that the proof-of-concept study will help Americans make an informed decision about what provides the best protection.
“If everyone were wearing a mask, we could stop up to 99 percent of these drops before they reach anyone else,” said study co-author Dr. Eric Westman, associate professor of medicine at Duke University, in a statement.
“If there is no vaccine or antiviral drug, it is the only proven way to protect others as well as yourself.”