N95 masks are the best. But if you manage to get one, it might be a fake.

When it comes to masks, the N95 is the gold standard.

Worn right, it fits tight. It filters out 95 percent of what’s floating around out there. It’s the mask you want firmly affixed to the faces of your frontline workers. The general public, alarmed by news of virus variants and calls for double-masking, wants them, too.

A year into the pandemic, N95s are still in demand. And at the same time, they’re being massively faked.

Millions of counterfeit N95s — masks that filter out 95 percent of airborne particles — have been seized by federal agents in recent weeks. Fakes have been sold to hospitals, medical facilities and government entities, and potential victims in several states have been warned they may have unwittingly paid for impostors.

The problem: Someone wearing what’s supposed to be an N95 could assume there’s more protection than exists. Fakes aren’t tested at strict N95 standards and could be risky for workers treating patients who have COVID-19.

“They’re extremely dangerous,” Steve K. Francis, an assistant director for the Global Trade Investigations Division of Homeland Security Investigations, said at a recent news conference. “They’re providing a false sense of security to our first-line responders, to American consumers.”

The Centers for Disease Control and Prevention doesn’t recommend N95s for the general public, saying those masks “should be reserved for healthcare workers.” Though the initial scarcity of N95s has eased, medical personnel have reportedly been re-using the masks, even though they have generally been considered a one-time use product.

The CDC does say that people who use public transportation, take care of someone with COVID-19, are at increased risk for illness themselves or work around lots of others — driving a bus or bagging groceries, for example — might consider masks with extra protection.

That can include KN95 masks, which are made in China and are similar to N95s. The U.S. Food and Drug Administration lists China-made masks authorized for use in the health emergency on its website.

But the CDC also warns that about 60 percent of KN95 masks in the United States are counterfeit and don’t meet N95 mask standards.

Real N95 masks are approved by the National Institute for Occupational Safety and Health and will have an NIOSH approval label on or in the packaging, as well as an approval number on the mask.

To spot fakes on websites purporting to sell N95s or on actual masks, the CDC says, look for bad grammar, typos, errors and claims of being “legitimate” or “genuine.” Other warning signs:

The primary contact email address for the seller’s website is a free email service.","type":"text

The seller claims NIOSH approval for a child’s mask. (NIOSH doesn’t approve masks for children.)","type":"text

The mask has decorative fabric or add-ons such as sequins.","type":"text

The mask has ear loops instead of bands that go around the head. (KN95 masks, however, have ear loops.)","type":"text

The CDC provides a list of approved N95s by manufacturer on its website, cdc.gov., as well as a graphic showing a mask with the approved markings on it.

The CDC provides a list of approved N95s by manufacturer on its website, cdc.gov., as well as a graphic showing a mask with the approved markings on it.

Even with the gold standard of masks, fit is as important as filtration, said Michael Teng, a virologist at the USF Health Morsani College of Medicine.

If air escapes out the sides, the mask isn’t doing the job. In fact, some health care workers get fitted for their N95 masks — in Teng’s case, exposed to a foul-smelling chemical to see if it permeated. (It didn’t.)

“If it doesn’t suck onto your face as you breathe in, it’s not going to be useful,” he said.

The CDC offers plenty of advice about other masks.

A cloth mask should be multi-layered with a nose wire and thick enough to block light when held up to a bright light source. Disposable masks should also be multi-layered and nose-wired.

“The surgical mask is pretty effective, particularly if you get it to fit your face,” Teng said.

His tip: Knot the the ear loops near the face, where air can get in, so the mask fits snugly. A YouTube video from UNC Health shows how to similarly adjust an ear-loop mask to make it up to 20 percent more effective.

The CDC also gives thin masks and masks with exhalation valves or vents a big thumbs down.

And no, wearing a mask below the nose does not work. “It’s like chin-masking,” said Teng.