This kind of mask can actually spread the coronavirus. Here’s how to fix it

SAN FRANCISCO —  There’s a certain kind of N95 mask that’s actually bad to wear for public health during the COVID-19 pandemic.

San Francisco’s health officer warns that N95 masks with a vent on them allow a person’s germs to spread, rather than containing them close to the wearer’s face.

The warning is in the San Francisco health order, which says that any mask with a one-way valve — designed to facilitate easy exhaling — “allows droplets to be released from the mask, putting others nearby at risk.”

“As a result, these masks are not a face covering under this order and must not be used to comply with this order’s requirements,” said the health order, signed by Dr. Tomás Aragón, the health officer for San Francisco.

Exhalation vents can make the face cooler and reduce moisture buildup inside a face covering, the U.S. Centers for Disease Control and Prevention said — but the vents allow unfiltered exhaled air to escape. That defeats the point of wearing a mask for the coronavirus, which is to keep potentially infectious oral droplets from spraying outward to other people.

To convert the N95 masks that have vent holes in the front, simply place a piece of tape over the external vent to cover it, health experts said.

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As many as 20% to 50% of people infected with the coronavirus may never show severe signs of illness yet can still infect others. That’s why, health officials say, it’s so important to wear masks to keep the pandemic under control. It’s no coincidence that many nations that haven’t seen a sustained, out-of-control spread of the coronavirus have a public that universally wears masks when outside the home, experts say.

San Francisco and other health officials around the country have urged the public to wear cloth face coverings to reduce the spread of the coronavirus. A couple dozen California counties require the wearing of masks while in public — including Los Angeles, San Diego and Sacramento counties, as well as the nine-county San Francisco Bay Area — while other areas have made it a recommendation.

But there has been a backlash in a number of California counties, and officials have rescinded requirements to wear a mask. The latest to do so was Orange County, California’s third-most populous county.

In general, officials suggest members of the public wear cloth face coverings, rather than N95 and surgical face masks that should be reserved for healthcare workers.

“If you are currently using a medical mask, keep using it as long as you can. Only throw it away when it gets dirty or damaged,” the San Francisco health department said.