(CN) — Doubling up on cloth and surgical face masks can give twice as much protection as using a single mask, the Centers for Disease Control and Protection reported Wednesday.
Laboratory experiments conducted by CDC scientists showed that wearing a cloth mask over a surgical mask, or modifying masks by “knotting and tucking,” help to seal gaps around the edges, through which virus particles can flow.
Researchers assessed how effective it was to wear each of three options: a three-ply surgical mask, a three-ply cloth mask, and both.
Surgical and cloth masks, respectively, blocked 42% and 44.3% of particles from a simulated cough, while wearing both masks blocked 92.5% of particles.
A second experiment measured what happened when the doubled masks were modified by knotting and tucking, which involves “bringing together the corners and ear loops on each side, knotting the ears loops together where they attach to the mask, and then tucking in and flattening the resulting extra mask material to minimize the side gaps.”
Researchers ran 15-minute simulations on mannequin heads, modeling different mask arrangements for both the source and receiver of particles expelled from coughing.
When one party was unmasked, but the other wore either a double mask or a knotted and tucked surgical mask, exposure was reduced by around 80% and 60%, respectively.
Protection jumped when both parties were wearing a double mask, blocking 96.4% of particles, or knotted and tucked masks, which blocked 95.9%.
“This observation suggests that modifications to improve fit might result in equivalent improvements, regardless of the masks’ baseline filtration efficiencies,” the report states.
CDC researchers noted that there is variation among cloth masks you can buy, so the simulations can’t be assumed to represent real-world settings.
The findings also may not carry over for children or people with facial hair, which can change the way a mask fits.
The CDC study builds upon previous research into the most protective face mask styles.
In a September 2020 study of commonly available mask types, Duke University researchers shined laser beams on water particles from a spray bottle that passed through various materials.
The Duke researchers found that some options are nearly as protective as standard surgical masks — while others, “such as neck gaiters or bandanas, offer very little protection.”
In fact, the data showed that people wearing a neck gaiter actually had higher transmission rates compared to wearing no face covering. The researchers attributed that to the coverings breaking up bigger droplets into smaller ones that can scatter farther.
Since early April 2020, the CDC has recommended wearing a cloth face mask to protect against Covid-19. At the time, however, the agency’s guidance sent mixed signals when paired with messaging from the president and vice president.
Former President Donald Trump had said it wouldn't be a good look for him to wear a face mask.
“I just don’t want to wear one myself,” Trump said at the time, while acknowledging the CDC’s recommendation. “I think sitting behind that great resolute desk, wearing a face mask as I greet presidents, prime ministers, dictators, king, queens, I don’t see it for myself.”
And weeks after the CDC guidance came out suggesting masks for everyone — previous guidelines applied only to those with Covid-19 symptoms — former Vice President Mike Pence, head of the Trump administration’s coronavirus task force, came under fire after refusing to wear a face mask during a tour of the Mayo Clinic.
On his first day in office, President Joe Biden signed an executive order requiring masks to be worn by on-duty federal employees and contractors, and by all people on federal grounds and in buildings.
As of the beginning of February, 14 states and the District of Columbia had universal masking mandates, according to the CDC.
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