N95 masks most effective, but cloth masks work, too, according to researchers

Although N95 masks are most effective in blocking the transmission of the coronavirus, cloth and surgical masks also help, especially if everyone in a room is wearing them, experts and multiple studies say.

Masking in schools has been debated over the past week, after Nassau County Executive Bruce Blakeman said most masks are ineffective while voicing his opposition to the statewide indoor mandate. Blakeman issued an executive order Jan. 6 telling schools they are free to ignore the mandate, although Gov. Kathy Hochul, the Nassau-Suffolk School Boards Association, the state Department of Education and others have said Blakeman doesn’t have the legal authority to override the state rule.

Jack Caravanos, clinical professor of environmental public health sciences at the NYU School of Global Public Health in Manhattan, said although N95 masks clearly are more protective than cloth masks, especially with the highly contagious omicron variant, they have one big advantage: "The cloth masks are comfortable, and if they’re comfortable, more people will wear them."

N95s are effective largely because, if worn correctly, they fit tightly, but because of that tight fit, "It’s not a very comfortable mask," said Caravanos, who said he sometimes wears cloth masks.

Blakeman said parents should decide whether their children wear masks. But that decision potentially impacts the health of other children, experts said.

The risk a mask-wearing child will contract the coronavirus rises "significantly" if a nearby infected child not wearing a mask is breathing or talking, and is facing the mask-wearing child, said Ali Khosronejad, an assistant professor of civil engineering at Stony Brook University who studies mask effectiveness.

If five people are in a room, "The risk any one of those people would get infected goes way down" if one person has COVID-19 but all five are wearing masks, because there would be fewer infectious particles in the air, Caravanos said.

He said mask-wearing generally is more important among young schoolchildren than among adults, because kids are more likely to do things that emit more droplets and aerosols that could contain the coronavirus.

"I probably would say that if my students weren’t wearing a mask, it’s no big deal," said Caravanos, who wears a mask while teaching. "If I were an elementary school teacher and the students weren’t wearing a mask, it is a big deal, because they’re talking and screaming and playing, versus college kids, who will sit there and take notes quietly, with very few aerosols being generated."

Research last summer and in 2020 led by Khosronejad found that even normal breathing can lead to a "jet of saliva particles" invisible to the naked eye that can travel more than 9 feet.

Indoors, "Just wearing a cloth mask, you can curb the spreading to less than 2 feet away from the person," Khosronejad said.

N95s are the most effective masks in blocking the spreading of saliva particles and in preventing the inhalation of the particles, followed by KN95s, surgical masks and cloth masks, he said.

The research was done pre-omicron, but, he said, "The physics of saliva particle transport should be similar for various variants." In addition, although the contagiousness of omicron means that cloth and surgical masks in particular are less effective with omicron than with other variants, they still help reduce the inhalation of particles, and are better than no mask at all, he said.

A 2020 study by researchers at Northeastern University in Boston found that fabric masks varied greatly in effectiveness depending on the fit and shape of the mask, ranging from less than 30% removal of particles to nearly 90%.

A tighter fit and filtering material is why N95s are better than other masks, Caravanos said.

"It’s all about leakage" of air from the neck and cheek areas, he said.

N95s have straps that go on top of the head and neck, so "you’re putting pressure so the mask sticks to the face much better," he said.

KN95s have similar filtering ability as N95s, but they typically use ear straps, and ear straps don’t provide as tight a fit, Caravanos said.

For any type of mask, users can check the fit by putting fingers near the nose "to see if air is rushing out," or by seeing if glasses fog up, he said.

For some people, including those with a low or excessively high nose bridge, fits may be less tight, he said.

Wearing a cloth mask over a surgical mask — especially if the cloth mask covers the surgical mask entirely — improves protection, Caravanos said.

Centers for Disease Control and Prevention guidance calls for wearing masks with two or more layers of washable, breathable fabric that covers the mouth and nose, can be secured under the chin and fit snugly — with a nose wire to help prevent air from escaping.

But The Washington Post reported late Monday that the CDC is considering changing the guidance to recommend people wear N95s or KN95s if they’re able to do so consistently and correctly.

The CDC did not initially recommend N95s for the public because of supply shortages for health care workers. N95s are now widely available.

In addition to claiming most masks aren’t effective, Blakeman said they can harm children’s breathing and potentially lead to long-term medical problems.

But Caravanos said there’s no evidence masks harm children’s or adults’ health.

"All of that has been disproven," he said.