Fake N95 masks have flooded the market. Here's how to tell the difference

(CNN) There's one mask guideline that hasn't changed throughout the pandemic -- you definitely should be wearing one.

But what happens when you're not sure if your mask is real?

Between the time the pandemic began and the year ended, US Customs and Border Protection (CBP) seized over 14.6 million counterfeit face masks entering the US, the agency told CNN.

N95 masks are considered the gold standard for mask usage, but counterfeit doppelgängers may threaten Americans' safety. Not meeting US safety standards means they may not filter out airborne particles effectively, the agency said.

N95 masks can also be mistaken with KN95 masks, which meet standards in China yet are not certified by the US National Institute for Occupational Safety and Health.

Here's how you can spot a fake N95 mask.

The most important thing: NIOSH approval

The National Institute for Occupational Safety and Health is a part of the US Centers for Disease Control and Prevention that focuses on worker safety and health.

Before filtering facepiece respirators -- a fancy term that includes N95 masks -- can be used in any workplace, they must be certified by NIOSH.

For an N95 mask to get a NIOSH stamp of approval, it needs to filter at least 95% of airborne particles.

When finding out if an N95 mask is fake or not, NIOSH markings are your compass. But there's some vetting you can do before you even have a mask in hand.

What to consider before you buy

When buying masks online, there are a few things you can ask yourself, according to CDC guidance on spotting fake PPE.

If you're buying directly through a website:

• Are there typos, bad grammar or other errors on the site?

• Are there website flaws, like unfinished or blank pages, dummy text, broken links and misspelled domains?

If you're buying through a third-party marketplace:

• Does the listing call the product "genuine" or "real"? Legitimate companies don't need to tell buyers their products are real -- at least not in the product name.
• Have reviews been left on the product, or on the seller? Buyers unhappy with the product may reveal that it is poorly made or illegitimate.
• Is the price too good to be true? It probably is.
• Is the seller selling the same items over time, or keeping with trends? Legitimate businesses tend to stay consistent.
• Does the seller put their contact information in images? If so, they may be skirting around marketplace policy to keep interactions between buyers and sellers on the site.

How to check if your mask is real

Okay, but what if you've already bought masks off a website or marketplace and don't know if they're the real deal?

Here's your rule-of-thumb: No markings means no approval.

NIOSH-approved masks have an approval label on or within the mask packaging -- either on the box or in the users' instructions. The mask should also have an abbreviated approval marking.

The approval number on your mask should begin with "TC." The mask should also have a NIOSH logo printed on it. This image from the CDC can help you identify your mask's markings.

Then, you can check for the approval number on NIOSH certified equipment list.

Some other red flags to look out for include:

• Any decorative elements, like sequins.
• Ear loops instead of head bands. Head bands are crucial to the N95's tight fit.
• Claims for the approval for children. NIOSH does not approve masks for children.

Got a real mask? Share these resources

The CDC and NIOSH have resources to help you in spotting counterfeit masks, or even other PPE and medical gear. You can start here and get more tips on vetting masks. You can also look through photos of non-NIOSH-approved masks.

Then, you can read about how to protect yourself from buying counterfeit goods.

Got a fake mask? Report it

Fake masks aren't the only counterfeit products being sold, nor the only scam to capitalize on the pandemic.

Criminal organizations are also trying to sell counterfeit pharmaceuticals, other PPE and medical devices to "unsuspecting American consumers," CBP Executive Director for Trade Policies and Programs, John Leonard, told CNN.

Covid-19 has been a fertile time for other scams of all kinds to proliferate -- most recently regarding vaccines.

While staying aware and keeping up-to-date, you can report any counterfeit masks to CBP through their reporting system, or by calling 1-800-BE-ALERT.

You can also report to the National Intellectual Property Rights Coordination Center online, or by telephone at 1-866-IPR-2060.