- U.S. health workers have been dealing with a shortage of N95 masks since March, when the coronavirus began to spread rapidly.
- A study of 29 types of masks used in healthcare settings found that expired and used N95s block coronavirus particles just as well as newer ones.
- Surgical masks block fewer particles than N95s, but are still effective.
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The US has spent months dealing with shortages of N95 masks – the type that works best to protect people from the coronavirus. Healthcare workers had to deal with expiration and used N95s despite questions about their effectiveness.
Now, those workers may be able to breathe a little easier: A study published Tuesday in the journal JAMA Internal Medicine found that used and expired N95 masks can be just as effective as new ones.
In the study, researchers at the University of North Carolina, Chapel Hill, tested the filtering ability of 29 types of face masks commonly used in hospital settings, including new, expired and used N95 masks, such as surgical masks with bands and ear loops.
The results showed that N95 masks – even expired and masks that were once used then sanitized and reused – worked much better than surgical masks, blocking almost all particles in the air. Surgical masks with straps offer better protection than those with ear loops, probably because they fit tighter.
Testing the masks: N95s performed better than surgical masks across the board
The researchers tested all 29 types of mask on a male volunteer, while a female volunteer tested six of the most commonly used masks. The study did not include cotton masks, bandanas, or other non-medical masks because the focus was on health care settings.
To assess each mask, the researchers filled a room with aerosolized salt particles roughly the size of small pieces of coronavirus, and then sent the volunteer to wear that mask.
Over the next three minutes, the volunteer would repeat a series of movements, designed to mimic the daily tasks of a health care worker: bend down and up, read, turn his head from side to side, and turn his head up and down.
At the beginning of 2020, the Strategic National Stockpile had barely 1% of the N95 masks expected to be needed by health workers.
Mike Segar / Reuters
Of all the types of masks commonly used in hospital settings, surgical masks with ear loops perform the least, protecting the male volunteer against only about 40% of particles. They protect the female volunteer of just under 27%.
Surgical masks attached to the back of the head did it better, accounting for nearly 72% of the particles.
As expected, all N95 masks (new, once used and expired) performed better than surgical ones. In each activity, they exceeded the number in their name, blocking more than 95% of the particles. In fact, none of the N95s block less than 96.8% of particles – not even decayed masks like those once sanitized with hydrogen peroxide and ethylene oxide.
What the findings mean for health care workers
The researchers warned that their findings may not be perfect because they test most masks on only one person, and masks fit people differently depending on their main shapes. This can mainly affect the security levels of surgical masks, as these are not like N95s.
But changing main forms would probably not change the researchers’ general conclusion: that both expired and lightly used N95 masks, if properly fitted and sterilized, are still worth using in healthcare settings.
In a commentary accompanying the study, Caitlin Dugdale and Rochelle Walensky, two infectious disease specialists at Harvard Medical School, asked for their own take on the findings.
“Importantly, no documented SARS-CoV-2 outbreaks have been linked to institutions in which surgical masks were used assiduous instead of N95 masks,” she wrote, “suggesting that even if air transport is a major participant for SARS-CoV – 2 transmission, surgical masks are probably enough to prevent it. “
The key, however, is that patients should wear the masks as well.
