By Alexandria Hoff

PHILADELPHIA (CBS) — Twenty airports in the United States are now screening some passengers for the coronavirus. It’s an effort aimed at preventing the spread of the potentially deadly illness.

But here in the U.S., another prevention tactic has caught on.

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As far as screenings go, passengers arriving on connecting flights from China will be screened by the CDC before leaving the international section of the airport.

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But something we have noticed here is that some travelers, even domestically, are donning facemasks, which are becoming harder and harder to come by.

Like many other local supply stores, Philadelphia’s Fairmount Hardware is suddenly facing a new kind of demand for masks, specifically the N95 model.

“Today we sold 41 boxes,” said Dave Arici, of Fairmount Hardware. “Yeah, 41 cases or 41 boxes of 20, back-to-back.”

This inventory squeeze coincides with growing concerns over the new coronavirus, especially after a handful of cases have landed in the U.S.

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According to the CDC, Americans should not feel the need to wear facemasks to prevent catching the coronavirus. In fact, there’s not much evidence that shows they help. Where they do serve a purpose is when worn on an already sick person.

“If they are feeling like they have symptoms, we do ask them to put on a mask when they are coming to waiting rooms or the emergency department or when they are going into a public space,” said Dr. Frank Esper.

“They want to know how much more we have in our warehouse because they want to buy the balance,” Arici said.

The demand locally remains but retailers suspect it’s not really for local use. Instead, customers are shipping the masks to relatives in Asia where they are largely sold out or selling them online.

“They are probably five, six times the price of retail right now on eBay. We saw a box of 20 on eBay right now for $149,” Arici said.

To put that in perspective, those boxes retail for about $24.

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Health experts say there is one clear benefit of wearing a facemask, which is it ensures the person wearing it will touch their face and mouth less.