Your Face Mask and Covering Questions, Answered

April 10, 2020

We went to the experts to answer your most pressing questions about face masks and homemade face coverings and how to best protect yourself and others from infection.

Anchor Stan Bunger of KCBS Radio posed listener questions to Dr. Scott Segal, chairman of anesthesiology at Wake Forest Baptist Health in North Carolina medical center in Tuesday's "Ask an Expert" segment at 9:20 a.m.

Dr. Segal launched a research project to study the effectiveness of materials used to make homemade masks.

Q: Let’s start with the backdrop here. In a hospital or medical environment, what are those masks made out of and is that commonly available stuff?

So hospital grade masks are really a fairly high-tech item, despite being made of what appears to be paper cloth. They have multiple layers, they have great filtering capacity, they’re easy to breathe through and they’re water-resistant. All of which makes them ideally suited for use in medical settings.

The sorts of masks that we’re talking about are the homemade masks, typically made of cloth materials you might find anywhere in your home or at a fabric store. And those are not currently being used in our hospital at this point. 

Q: Is it possible to come up with something that you make yourself that would be - not safe - but as effective as what medical people use?

That was actually what we set out to discover. So when we were worried about our supplies of masks at the hospital, we had a large group of volunteers who were willing to make cloth masks for us. And several hundred of them were manufactured and dropped off at the hospital, and we were going to use those as a backup plan.

What became clear to us was that they were made from a wide variety of different materials and different designs. And we felt that it would be important to try to understand which ones worked better than others. So we submitted them to testing primarily based on how well they filtered very small particles, like the size of viruses or bacteria, and we found that they varied quite wildly in their effectiveness.

Q: So let’s dig into that, let me start throwing a few listener questions at you and maybe the answers will become clear. Here’s the first one: I ordered a mask but it won’t arrive for 1-2 weeks. I’m about to cut up a t-shirt (my boyfriend’s t-shirt!), is that a good option?

Well we’re not sure, t-shirts are not one thing. The actual type of material probably makes a big difference. The generic advice that we’ve been giving folks is to take your fabric that you’re intending to make the mask from and hold it up to a bright light or the sun. If you can easily see the light passing through the fabric and illuminating the fibers, it’s probably not the best filtering material. 

If it’s a denser weave or a thicker yarn or material and it blocks more of that light, we think it’s probably going to be a better filter. And that was true of the masks that we tested. The ones that did a better job actually filtered small particles as well or even better than a traditional surgical mask. So that’s what we would recommend, if you can get your hands on it.

But I will say that something is better than nothing if you must venture out, so I wouldn’t discourage someone from using an old t-shirt if that’s all they can get their hands on.

Q: What is the best material then, in terms of commonly available material?

If you can get your hands on something called quilter’s cotton, that tends to be heavier weight, higher grade cotton fabric. It will have the characteristics we just discussed. This would be different from a simple printed cotton you might find in a discount fabric store. You can also use a lower grade cotton on the outside, and put a flannel inner layer, that also performs really well. 

But it’s difficult to say “use exactly this fabric or that” because not everyone has access to everything, and unfortunately lots of fabric stores are closed with stay at home orders. And so we recommend that people look for a fabric that might be in their home and make sure that it does as best as possible with this light test.

And then I have to add one other thing: no mask is good if you can’t breathe through it. So you’ve gotta hold it up to your mouth and nose, not for a breath or two but for several minutes, and make sure you can actually breathe through it. If the material is a great filter but you can’t comfortably breathe through it, you either won’t wear it or you’ll just breathe in and out through the sides and it’ll be less effective. 

Q: Let me be sure we have this right because you said quilter’s cotton - I happen to be married to a quilter so I think I know what you’re talking about. Some people may be thinking about the batting that goes inside a quilt, you’re talking about the cotton that goes on the outside is that right?

That is right, not the batting or the stuffing, it’s the outer layers. People who quilt will tell you it’s got a heftier weave and you can feel the difference with your hands. Even I, who knew very little about fabric prior to this, could learn to tell the difference. It’s relatively easy to do so I would ask a friend who sews if you need some advice. 

Q: My daily walk consists of a long block on a paved edge of our street and then two miles on a 10-foot wide gravel path. Very few people on it and plenty of room for social distancing which we all observe - is there any justification for wearing any mask? What’s the current thinking on the flight path of a forcibly ejected coronavirus?

Well these are great questions and I certainly wouldn’t consider myself an expert in that sort of material but I would say that the best evidence we have shows most particles carry about three feet or so, so they’re recommending six feet apart. Close contact is defined as within six feet for more than 10 minutes by health authorities. 

So I would say casually passing someone on your walk is not a major risk - and again this is not my area of expertise - but I would say that wearing a mask while doing an outdoor walk if there’s no one else around is probably overkill. Remember that the public health advice for wearing masks in public is really more to protect others, rather than the wearer, in case you happen to be infected and don’t know it. What we’re giving is advice that might protect the wearer as well. 

Q: This next one we can probably spin a bit: Is there any place either in person or online where I can purchase a homemade mask or a mask kit? One that does not require any sewing?

You can go on Etsy right now, and in fact I’m going to really annoy our producer Nic Palmer because Nic is a Dodgers fan and I have ordered two glorious looking San Francisco Giants logo masks that should be here in a couple days. Now I have ordered them - and based on what you’ve told us earlier the tests should be fairly simple, you hold it up to the light and see how sturdy they are. Is that something people could be asking the Etsy vendors?

Well I don’t want to annoy the Etsy vendors either but I think that that’s not a bad idea, to get some idea of what the fabric of their mask is made out of. Since we came out with this work, a torrent of people have been writing to me saying, “do you think this or that would be a good mask?” All I can offer is generic advice. Unlike medical grade materials there’s no formalized testing for fabrics so there’s no way for me to say, “use grade whatever and that what will work and others will not.” But it seems like a reasonable thing to ask.

Q: What do you need to do to disinfect these things? Are their best practices?

This is a wonderful question and I have to admit that we don’t know yet. We do know that repeated washing definitely changes the characteristics of the fabric; you know this if you wash new clothes or new sheets that they feel different after. What we don’t know yet is how many washings and under which conditions would degrade the quality of the filtering of the mask. That’s part of our investigation now. 

The advice that I have been hearing is wash them like you’d wash any other garment that you’d worn close to your body, like undergarments and so forth, which probably means you’d wash them after a day’s worth of wearing and use another one next time.

Another thing to keep in mind is moisture from your breath gets into the material and moisture makes any mask, even a hospital-grade surgical mask, less effective over time. it essentially allows the particles to pass more easily through the material.  

So at the very least let it dry between wearings. Either hang it up or do what we do at the hospital which is put it in a paper bag and let it dry for a for a few hours and then wear it again if you need. Not a plastic bag because that won’t let the moisture escape. I’d probably wash it periodically in ordinary washing.

Q: There’s that old phrase, sunshine is the best disinfectant. Does that work here?

I’m not sure. Certainly drying helps and putting it in the sunshine is going to help that dry faster. I don’t know whether the sunshine in and of itself has any effect.

We’ve been exploring in the hospital ways that we might re-process medical grade masks using either ultraviolet light or the vapor of hydrogen peroxide. These are not things people should try at home of course. But we’re all learning a lot about something we never thought we’d even ask, which is how can we make a mask last longer?

Q: And that brings us to the next question, can I just spray it down with disinfectant and let it dry?

Well you’ve gotta be careful about that. Some of these harsher disinfectants are not made to be inhaled. You would’t spray it near your face and then inhale, so you shouldn’t put it on a mask and then try to breathe it in. 

We don’t know about what we call ‘outgassing’, which is if you spray the chemical on the cloth and then put it on a little while later, are you going to be breathing in harmful chemicals? So I’d be pretty cautious about that. At this point we’d recommend wash it in the washing machine the way you would any other cloth item. 

Q: When can you take them off? Should you be wearing them all day every day? what environments would be the appropriate places to be wearing any of these homemade masks?

That’s a great question and I’m glad you asked it that way. The best way to protect yourself is to stay home and to socially distance. Masks are never going to be as good as that. 

So the answer is you only need to wear them for short periods of time when you absolutely must leave the house and potentially interact with others. So I would not recommend wearing these masks all day long, especially at home. 

If you must be out and about, you wear it when you might interact with others. Then when you get home, you should untie the mask or grab the mask by the ear loop and not by the face of the mask and then either let it dry or put it into the wash and wear another mask the next time.

Q: You touched on breathability - people have been asking about the propriety or advisability of wearing one when you go out for a run or a bike ride.

I can’t tell you for sure. Chances are, if you’re running or riding a bike you’re not going to be close to another individual so I would imagine the risk is quite a bit less but I couldn’t tell you for sure. Certainly from a public health point of view, if you’re coughing or sneezing on others, if you’re feeling that bad you shouldn’t be out.

If you’re otherwise feeling well, it’s hard for me to understand how briefly passing somebody on a run or a bike would be a big risk and it might make it harder to exercise. If you’ve never worn a mask you’ll find they’re not comfortable and it does take a little while to get used to.

Q: Should I put it in the microwave?

We can’t recommend that. I have no idea how radiation might impact the virus or bacteria. I’ve been hearing about all kinds of things people want to do to sanitize the mask. The best advice we can give at this point is wash it like any other garment you’d wear close to your body. 

Q: A lot of people have these ultraviolet or blue light devices that have been sold to disinfect smartphones and so on, what about those?

We haven’t tested that degree of UV light. The kind of stuff that is available to consumers tends to be lower energy UV light. I would say it couldn’t hurt, but I’m not going to recommend it. 

The kind that we are testing for medical use is the sort that you would use in a closed room with no windows and people inside: very intense UV light designed specifically for disinfection and it takes a while for it to be disinfective. So I cannot make a recommendation that those consumer-level devices would offer much protection and I certainly wouldn’t want people to have a false sense of security. 


After this segment was broadcast, KCBS Radio heard from several people who wanted to pass along additional information.

Janet is a Bay Area quilter who wrote to suggest mask-makers check out some detailed information put together by retired nurse practitioner Cindi Rang, who runs The Fabric Patch quilting store. Rang offers detailed information about fabrics and techniques on her website.

Gary suggested we take a look at those blue shop towels you can find at hardware stores and home centers, pointing us to an article about how they're being used in face masks.

John Muir Health offers this information for those wishing to make their own masks, as well as a sewing pattern.

Facebook | Twitter | Instagram