These masks are effective against omicron 0:49
As the US government begins to distribute free masks, you may be wondering: How long can I really wear an N95 and still protect myself and others from the risk of Covid-19?
"I use mine for a week," said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech.
The material and filtering ability of an N95 mask "will not degrade unless you physically rub it or put holes in it," Marr said.
"You would have to be in very polluted air... for several days before it lost its ability to filter out particles. So you can really wear them for a long time."
"People have been talking about 40 hours, I think that's fine. ... The straps will get too loose or maybe break before you lose filterability," he added.
The reason N95 masks are designated single-use is because they're categorized as medical masks, said Erin Bromage, an associate professor of biology at the University of Massachusetts Dartmouth.
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In medical settings, healthcare workers change masks more frequently to avoid "cross-contamination of a patient room with equipment that was used in the room of an infectious person and then moving on to the next room and bringing that infection with you," he said. "When you take something medical-grade that's single-use and put it out into the general public, we're not worried about you contaminating the different environments that you're in. It's really about giving you protection."
N95s "used to cost around $1 each," Bromage added, but prices have soared recently as public demand for these masks has increased amid concerns about the omicron variant.
If you reuse N95s safely, you get at least two to three days of use out of a mask, Bromage added, but "I know it's still an expense."
Some local public health departments, such as the Maryland and Milwaukee health departments, offer free N95 masks.
Here's what you need to know about how to safely use and reuse N95 masks.
Compared to cloth masks, well-fitting N95 masks better prevent tiny particles from entering the nose or mouth thanks to certain materials, such as polypropylene fibers, which act as mechanical and electrostatic barriers to shared air, the main driver of coronavirus infection.
The difference between N95 and KN95 masks is where the mask is certified, according to the Oklahoma state department of health.
The United States certifies N95s, while China approves KN95s.
About 60% of KN95 masks sold in the United States are counterfeit and do not meet the requirements of the National Institute for Occupational Safety and Health, according to the US Centers for Disease Control and Prevention.
"If they're made to the standard and certified by the appropriate boards in your country, like NIOSH here, they all do basically the same thing," Bromage previously told CNN.
"But there are a lot of knockoffs that aren't certified on the KN95 side, that may meet the standards but aren't certified to meet them. And there are others that clearly don't."
These masks are effective against omicron 0:49
N95 masks are "not made for children," Marr said.
"For older kids, my 10-year-old uses an N95 that comes in a small size (meant for adults)."
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"If you see an N95 as being marketed for children, that should raise a red flag," Marr added.
"There will be KN95s and KF94s designed and marketed for children. With those, it's the same issue that we discussed for adults, which is to make sure you get them from a reputable and trustworthy source, because there's a problem with fake KN95s that aren't as protective as they should."
The N95 Project, the National Clearinghouse working to provide equitable access to personal protective equipment and coronavirus testing, is a trusted source for N95 and KN95 masks, Marr said.
The KF94 are Korean standard masks.
You may need to try a few different brands or shapes of KN95, KF94 or small N95s to find one that fits and is comfortable for your child, Marr said.
If you're still having trouble fitting the mask to your child's face, you can tie the ear straps or use adjusters to make sure the mask sits tight enough, he suggested.
This CDC video on the knot and fold method might also help.
How to reuse an N95 mask (and when not to)
To reuse N95 masks in the safest way possible, avoid touching the outside front of the mask when you put it on, Marr said.
Instead, try to grab the edges or straps.
"Definitely avoid the part right in front of where you breathe, like right in front of your nose and mouth," she added.
Even after wearing an N95 in a crowded closed environment, like a subway, Marr said "these masks are really designed to handle a lot of particles and they will still work."
However, exposure to the virus should lead you to change care.
If "I was working in an office and I was wearing an N95 and someone in my office had tested positive, I would know I was well protected," Bromage said.
"But I would probably throw that mask away. Because that mask has done its job of trapping the virus and I don't even want to risk it being there and getting on my hands or whatever."
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You may have unknowingly been near an infected person in any other public space, such as a subway or grocery store, while wearing an N95 mask.
Staying at least 2 meters away from others as much as possible can help reduce the risk of covid-19.
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If the mask becomes wet, visibly dirty, folded, wrinkled or otherwise damaged, including from wearing makeup, you should replace it, as these conditions could decrease effectiveness, Marr and Bromage said.
"The longer you wear it, the more material it traps, which means the breathability, the strength of the mask starts to decrease," Bromage said.
"One of the first indicators of being able to change it if it looks nice and clean is that it feels a little harder to breathe. When there seems to be more resistance with each breath."
How to disinfect N95 masks
The longer and more often you wear an N95 mask, the more contaminated it can be.
But the particles will die over the course of a few to several hours, Marr said, and even faster if you set the face covering aside in sunlight.
"Things like temperature and sunlight have an effect, but you don't want to throw it in an oven or microwave," Bromage said.
"I used to stick mine on the dashboard of my car in the summer, and that would be more than enough for the heat and direct light it received. But really, there's nothing you can do to prolong its life through affordable cleaning for the average person.
Fake N95 masks have flooded the market.
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Because N95 masks have that special static charge that helps filter out viruses, you shouldn't wash them, as the water will dissipate the charge, Marr said.
In general, the risk of contamination from reusing N95 masks is "lower, much lower than the risk of not wearing an N95 and breathing in particles," Marr said.
"I don't want people to avoid using an N95 because they are concerned about contamination in an N95. The N95 will provide a significant net benefit."