NEW YORK & AMARILLO, Texas (AP/KAMR) — U.S. health officials on Friday encouraged more Americans to wear the kind of N95 or KN95 masks used by healthcare workers to slow the spread of the coronavirus.

Those kinds of masks are considered better at filtering viruses from the air, but they previously were in short supply, and Centers for Disease Control and Prevention officials had said they should be prioritized for health care workers.

In updated guidance posted late Friday afternoon, CDC officials removed concerns related to supply shortages and more clearly said that properly fitted N95 and KN95 masks provide the most protection.

Dr. Rodney Toung with Texas Tech Physicians Family Medicine explains the difference between the N95 and KN95.

“A KN-95 mask is not certified for medical use and the way that the N95 is, but their construct in terms of the mask itself, the filtration properties are quite similar does a very good job,” Dr. Young said.

The next step below the N95 and KN95 masks are surgical masks.

“Those provide a good level of protection, but in their core, surgical masks are designed to protect others around you since, at the time of surgery, we’re thinking we’ll make to keep from putting our patients at risk,” added Dr. Young.

Then you move into cloth masks with multiple layers and pockets for filters, which Dr. Young said provides a better level of protection than thin cloth masks and bandanas.

“Oftentimes, they [thin cloth masks] are marketed or reviewed online as ‘how wonderfully breathable they are, it’s almost like having no mask at all.’ And in fact, they’re telling you the truth, it is almost like having no mask at all,” said Dr. Young.

“Ideally, in order to create the environment that creates maximum filtration, there needs to be a good seal on the perimeter of the mask. That’s why the surgical masks and the cloth masks that are just not engineered to be able to provide that seal will never provide the same level of protection as the masks that are designed with the seal in mind,” Dr. Young said.

Agency officials noted some masks are harder to tolerate than others, and urged people to choose good-fitting masks that they will wear consistently.

The CDC has evolved its mask guidance throughout the pandemic.

In its last update, in September, CDC officials became more encouraging of disposable N95 masks, saying they could be used in certain situations if supplies were available. Examples included being near a lot of people for extended periods of time on a train, bus or airplane; taking care of someone in poor health; or being more susceptible to severe illness.

On Thursday, President Joe Biden announced that his administration was planning to make “high-quality masks,” including N95s, available for free. He said more details were coming next week. The federal government has a stockpile of more than 750 million N95 masks, the White House said.

The latest CDC guidance notes that there is a special category of “surgical N95″ masks, that are specially designed for protection against blood splashes and other operating room hazards. Those are not generally available for sale to the public, and should continue to be reserved for health care workers, the agency said.