Why most of us should be wearing N95 masks

N95 respirators have long been the best disposable face coverings for protection against airborne viruses, but until recently, they were scarce.

When worn properly, N95s can filter out at least 95% of particles in the air, including the virus that causes COVID-19. Only pricey air-purifying respirators or hazmat suits offer better protection.

Early in the pandemic, the U.S. stock of N95s was too depleted even to meet the sudden, dire needs of front-line health-care workers. The Centers for Disease Control and Prevention told us to save the most protective masks for essential workers and sew our own.

After two years of ramped-up production, high-quality N95s are widely available to consumers, and the Strategic National Stockpile contains more than 750 million.

Some experts recommended that more people wear them after the delta variant emerged last summer, and on Jan. 14, the CDC updated its recommendations to tout their effectiveness and remove caveats about short supply. The White House plans to give away 400 million N95s in the next few weeks to help stifle the spread of the highly transmissible omicron variant of the novel coronavirus.

How do N95 masks work?

N95s come in several shapes and carry a mark from the National Institute for Occupational Safety and Health (NIOSH) to show that they are authentic. Some look like domes, others a bit like duck bills. This flat-fold, three-panel type is popular in hospitals.

It is made of polypropylene fibers that are 1/50th the size of a human hair, blown together in a random web to create an obstacle course for particles.

Air flows in and out of the microscopic spaces between the fibers, allowing the wearer to breathe.

The fibers carry an electrostatic charge that attracts passing particles like a magnet. Large particles bump into the fibers and easily become trapped. The more particles are captured, the denser and more effective the fibers become.

The tiniest particles can move between fibers, but they are constantly jostled by air molecules. All that pinging around makes them likely to eventually hit a fiber and become trapped as well.

The most difficult particles to capture are small enough to slip between fibers but stout enough that they don’t bounce around a lot. Coronaviruses typically fit into this midsize category. However, the electrostatic charge is effective at grabbing particles of all sizes out of the air.

Who should not wear an N95?

Nearly everyone over age 2 needs to wear a mask in at least some situations, but the CDC stopped short of recommending that everyone switch to N95s, saying basically that the best mask for you is one that fits well and that you’ll wear consistently.

For instance, if you find N95s uncomfortable, or you prefer ear loops to head straps, maybe you’re willing to sacrifice a bit of protection.

According to the CDC, well-fitting N95s are the most protective, followed by KN95s and surgical masks. Chinese-made KN95s are supposed to be of a standard comparable to N95s, and many are of high quality, but they do not go through the NIOSH approval process. “Loosely woven cloth coverings” are the least protective.

Beware of the many counterfeit N95s and KN95s on the market. The CDC website has a list of approved models and examples of counterfeits. There are no NIOSH-approved N95s for children, although some manufacturers claim their products meet N95 standards. Children under 2 should not wear masks at all, and people with certain disabilities may not tolerate them.

For everyone else who wants one, there should be enough N95s to go around.

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The Washington Post’s Jessica Contrera contributed to this report.