(Bloomberg Opinion) -- A procedural mask loosely covers the mouth and nose of the wearer and has straps that go over the ears. The term is often used interchangeably with “surgical mask,” but among U.S. medical suppliers a surgical mask is one with ties secured behind one’s head for a snugger, more secure fit. Both are usually made of three or four layers of non-woven fabric, with one of the middle layers a melt-blown polymer that acts as a filter, and both are intended to be disposed of after use.

The surgical mask is meant for operating rooms and other sterile environments, procedural masks for areas that need to be clean but not necessarily sterile. Both give wearers some protection from things that might splash into their mouths or noses, but their main role in a medical context is to protect patients from what might come out of the nose or mouth of the wearer.

N95 masks, usually marketed as respirators by U.S. medical suppliers, have a different purpose — preventing those who wear them from breathing in small airborne particles (the N95 means that they’re supposed to filter out at least 95% of such particles). Construction workers wear them to keep out dust, firefighters wear them to keep out smoke, inhabitants of some cities wear them to keep out air pollution, and medical practitioners wear them to keep out bacteria and viruses from highly infectious patients. Most are made of spun-bonded polypropylene, and they tend to be stiff, not super-comfortable and a little hard to breathe through. If you don’t put them on just right, you also forgo much of their protection.

I offer this primer (which is not based on great expertise, so please let me know if I got anything wrong, or if you can explain to me how melt-blowing works) because health officials in Western countries have been giving some pretty confounding advice about the use of masks in fighting the coronavirus pandemic. For example:

As many people responded to Surgeon General Jerome M. Adams’ tweet, and sociologist Zeynep Tufekci summed up in a New York Times op-ed article last week: “How do these masks magically protect the wearers ... only if they work in a particular field?”

The answer is that there’s no magic. N95 respirator masks can protect their wearers even if they’re not health-care providers, and it’s not that hard to put them on correctly. The problem is that the nation’s hospitals have been running out amid a crush of coronavirus patients, and the people working there really ought to get first priority. Also, having tried wearing N95 masks during past visits to polluted Chinese cities and having found the experience so unpleasant that I decided to suck in deadly particulates instead, I am dubious that many people not in situations of intense peril would really wear the things consistently enough to protect themselves.

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Procedural and surgical masks are cheaper and more comfortable than N95 masks. They don’t offer much protection from disease for their wearers, but do seem to protect everybody else from wearers with infectious diseases. Their widespread use in China and several other Asian countries since January is increasingly being credited with slowing the spread of Covid-19 there. If Western countries want to restart their economies safely if and when the stay-at-home orders succeed in halting the spread of the virus, the wearing of such masks should probably be strongly encouraged.

Only … they’re in short supply now too, with hospitals being forced to sew their own surgical masks and the Centers for Disease Control and Prevention suggesting that in a pinch maybe a bandanna will do. Production is ramping up, but the demand is worldwide and most are made far from the U.S. (this is somewhat less true for N95 respirators, of which Minnesota-based 3M is a leading manufacturer), so I’m not expecting drugstore shelves here to be full of them any time soon. I checked online to see if the Walgreens Earloop-Style Face Mask could be purchased at any of the company’s stores right now, and the answer seems to be no, they’re sold out pretty much everywhere.

According to the Walgreens Covid-19 information page, meanwhile, it’s a “fact” that “Face masks will not prevent COVID-19 spread. Only patients with confirmed cases of COVID-19 and healthcare workers caring for them should wear masks.” Again, as in the surgeon general’s statement, the argument seems to be that face masks don’t stop Covid-19 from spreading, except when worn by certain people. Which is of course nonsense.

The concern that panic buying of surgical masks will keep them out of the hands of those who need them most is, on the other hand, not nonsense. It was shared by officials in Singapore early in the spread of what they called the “Wuhan virus,” with one government minister reportedly expressing consternation at Hong Kong Special Administrative Region Chief Executive Carrie Lam’s practice of wearing masks in her public appearances, saying that if he and his colleagues did that the Singapore hospital system “would have broken down” because of mask shortages. Instead of telling people not to wear masks, though, Singaporean authorities announced at the end of January that they would be giving four procedural masks to each of the nation’s 1.3 million households (about two-thirds of whom eventually took the government up on the offer), and asked that they be used sparingly. “You only wear a mask if you are not well and you have to go out to see a doctor,” said National Development Minister Lawrence Wong. “Those who are well do not need to wear a mask.”

As a statement of priority that’s fine, but given that there’s some evidence of the new coronavirus being transmitted by people who haven’t developed symptoms yet, it does seem like it could help if mask-wearing were more widespread than that. The head of the Centre for Infection at the University of Hong Kong suggested last week, for example, that non-mask-wearers be banned from public transit there for the time being. In Japan, where mask-wearing has long been common, it seems to be one of the most plausible explanations for why the new coronavirus has spread so slowly amid a government response less vigorous than what is now being seen in much of the rest of the world.

The wearing of surgical masks in Japan dates back to the influenza pandemic of 1918-19, according to a brief 2014 history by journalist Jeff Yang in Quartz. By the end of that pandemic, mask-wearing was common all over the world, including in the U.S., but in Japan a major earthquake and subsequent fires in and around Tokyo in 1923 led people to get their old flu masks out of storage to protect against the smoke and ash. Another flu epidemic in 1934 “cemented Japan’s love affair with the facemask,” Yang wrote, “which began to be worn with regularity during the winter months — primarily, given Japan’s obsession with social courtesy, by cough-and-cold victims seeking to avoid transmitting their germs to others, rather than healthy people looking to prevent the onset of illness.”

The practice then spread elsewhere in East Asia, with big boosts in recent decades from the Severe Acute Respiratory Syndrome outbreak of 2003 and China’s huge air-pollution problems. (Surgical and procedural masks don’t give as much protection against airborne particulates as N95 masks do, but they do give some.) The result was that most people in most East Asian countries seem to have already had a box of procedural masks or the like in the closet before the new coronavirus made its appearance, and that manufacturers in the region already had reason to make far more such masks every year than was needed just to supply the health-care sector.

Given the lack of such consumer demand in the West in the past, it shouldn’t be that big a surprise, or that big an indictment of our politicians and public-health authorities, that we can’t even contemplate having enough procedural or surgical masks for everybody to wear anytime soon. This is no reason to deny that masks can be useful, though.

It’s also no reason to despair. Home-made cloth masks, scarves and bandannas aren’t as effective at keeping germs in as three-ply disposable surgical masks are, but they aren’t totally ineffective, either. They also serve the same signaling purpose that masks seem to in Japan and elsewhere — steer clear, I might be contagious. I have a slight fever at the moment, and have been wearing a bandanna over my mouth and nose when I take the dog out for walks. People give me a pretty wide berth!

Also, if we’re lucky enough that the spread of the coronavirus slows during the Northern Hemisphere summer, some Western countries maybe just could, with government encouragement, have enough procedural masks on hand for widespread public use during its likely fall rebound. Then, after Covid-19 has been vanquished or at least rendered relatively harmless, we Westerners might want to consider getting into the habit of putting on procedural masks to go out in public whenever we have a fever or even the sniffles. I’m guessing it could save thousands of lives even in normal flu seasons, and would leave us far better prepared for the next pandemic.

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

Justin Fox is a Bloomberg Opinion columnist covering business. He was the editorial director of Harvard Business Review and wrote for Time, Fortune and American Banker. He is the author of “The Myth of the Rational Market.”

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