Free N95 masks, supplied by the U.S. government in an effort to fight COVID-19, are starting to arrive at Minnesota pharmacies.

The Biden administration announced this month plans to distribute some 400 million N95 masks for free through drug stores and community health centers, with quantities at pharmacies limited to three per person.

Retailers say availability may be scattershot in the coming days while supplies build.

"This is the largest deployment of PPE — personal protective equipment — in U.S. history," Jeff Zients, the White House COVID-19 response coordinator, said during a briefing this week.

When properly fit, N95 masks approved by the National Institute for Occupational Safety and Health filter out 95% of particles in the air. Rather than looping behind the ears, straps on most U.S.-approved respirators extend to the back of the head — one situated below the ears, and the other stretched across the crown.

Better access to N95s as a way to combat the pandemic is long overdue, said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

Enhanced protection with the masks remains crucial even amid signs of a peak in cases from the omicron surge, Osterholm said. Many people are still getting infected and it's not clear how long elevated transmission rates — with all their implications for deaths and hospitalizations — might continue.

"I think this is a very important step forward," he said. "You achieve a substantial improvement in protection by wearing a tight-fitting N95 respirator."

Hy-Vee started receiving shipments of the masks last Friday and most of the grocery chain's 275 pharmacies across the Upper Midwest are distributing the face coverings, said Christina Gayman, a spokeswoman for the Iowa-based retailer. Social media reports surfaced Wednesday of shoppers finding free N95s at some Minnesota Hy-Vees.

At CVS Health, inventory was expected to begin arriving in Minnesota as early as Thursday at stand-alone pharmacies and locations inside Target stores. Visits to four CVS locations in St. Paul on Thursday morning, however, found no free masks yet available.

Coborn's was expecting N95 masks to arrive at warehouses as soon as Thursday, but they likely won't reach store shelves until early next week, said Dennis Host, spokesman for the St. Cloud-based chain of supermarkets.

Most pharmacies that participate in the federal government's push to administer COVID-19 vaccines also will distribute N95s, the Wall Street Journal reported this week. The White House says shipments to Walmart have started. Walgreens has said it will participate.

Customers won't need to show ID or register in advance, pharmacies say.

At CVS, customers can request masks at the front-of-store checkout. Posted signs will indicate N95 mask availability. At the company's pharmacies in Target stores, free N95 masks will be available at the pharmacy counter.

Gayman of Hy-Vee said via e-mail that "most of our stores have a table set up near the pharmacy with a designated employee handing them out to customers."

Separately, the Walz administration said Thursday the state would provide 2.1 million KN95 masks — another filtering type of face covering that meets international standards — to community groups, local public health agencies, schools and other entities.

Earlier this month, the federal Centers for Disease Control and Prevention (CDC) said in updated guidance that N95 and KN95 respirators are examples of face coverings that provide better protection than others against COVID-19.

Maplewood-based 3M is the nation's largest manufacturer of N95s. Osterholm of the U has repeatedly advocated for the wider use of better respiratory protection devices, including N95s, throughout the pandemic.

People can re-use N95s so long as they aren't soiled or damaged, Osterholm said, adding that he often uses his respirators "for days and days." The masks work well, he said, because they're tight-fitting and made from special material with an electrostatic charge.

"That's what people don't understand — it's that these function just totally different than a, say, a cloth face covering, a surgical mask or any other piece of material like that."

Health officials add, however, that surgical and well-made cloth masks still have a role to play in efforts to contain the pandemic, especially for those who cannot tolerate high-filtration masks.

"When you talk about masks, they're only effective if you have them on your face," said Dr. Priya Sampathkumar, an infectious disease specialist at Mayo Clinic. "I continue to maintain that the mask that covers your nose and mouth all the time is better than having the N95 that is so uncomfortable that you keep taking it off."

Early in the pandemic, N95 masks were in short supply, so health officials cautioned they should be reserved for hospitals. Over time, supplies rebounded.

With the omicron wave, several municipalities have instituted mask mandates, with some — including Minneapolis — recommending the use of higher-quality masks.

The Minnesota Department of Health recommends wearing a high-quality mask, such as N95 and KN95s. Those masks, in particular, are very good at blocking droplets, the Health Department says.

"If you do not have this type of mask, wear a mask with two or more layers of tightly woven fabric," the Health Department says. "You can also layer a disposable mask under a cloth mask to increase effectiveness. The cloth mask should press the edges of the disposable mask snugly against your face."