Two masks or one? How many layers, and which fabric? Here’s everything you need to know before you start double-masking
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As cases of coronavirus continue to surge across the nation, many have made the decision to start doubling up on face masks if they have to leave the house. Dr. Anthony Fauci recently discussed the trend on the Today show and during a town hall appearance on CNN. Even President Biden and Vice President Kamala Harris are often seen with surgical masks underfabric face coverings while out and about in public. But the question still remains even as the idea gains more traction—just how effective is double-masking, really?
Almost a year into the pandemic, there is now a seemingly endless variety of face mask options available, from lightweight picks for sports, heavy-duty fabric masks for colder weather, and even more stylish additions. Many masks on the market right now are non-medical, so while they may be sufficient for a walk in the park or a socially-distanced meeting with friends outside, they’re not designed with frontline workers, doctors, or nurses in mind. Even if you’re not deemed an essential worker, non-medical masks don’t always offer sufficient filtration if you’re going to be in an indoor environment for extended periods of time. That’s where double-masking comes in.
While the CDC hasn’t taken an official stance on double-masking yet, we’ve asked experts to weigh in on how to double-mask properly, the effectiveness of double-masking versus single-masking, and what the best face masks are if you’re making the choice to double up. Here’s what to know.
Single-Masking vs. Double-Masking
As far as just using a single-layer mask goes, understand that they may only be appropriate under certain circumstances. “Single layer masks are most effective at minimizing spread of virus when worn by someone who is potentially contagious,” says Dr. Michelle Prickett, Associate Professor of Medicine (Pulmonary and Critical Care) at Northwestern University Feinberg School of Medicine. “Single-layer cloth masks are less likely to provide protection to the wearer and may be best-suited for outdoor activities, or when universal masking is being used with lower risks of spread.”
If you’re only wearing one mask, experts say the most effective face mask that stands on its own is a protective N95 respirator, often referred to as just an N95 mask. “The gold standard for effective particle filtration is the N95 masks used for medical purposes in the US while NIOSH-certified KN95 [masks] may also filter out 95 percent of particles,” says Prickett. With multiple layers of fabric, as well as an extra-tight fit around the face and neck, these masks defend well against the airborne particles and droplets that you breathe in.
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Dr. Stuart Cohen, Chief of Infectious Diseases and Director of Hospital Epidemiology and Infection Control at UC Davis, says that while no one currently knows exactly how many virus particles are necessary to infect someone with SARS-CoV-2, “masks provide an obstacle course for the droplets to get out or to get in. They don’t totally block everything; it’s just trying to make it harder for the virus particles to get through. So the tighter the weave of the mask, the better the quality, the less likely things are gonna get through.” What that means: you shouldn’t count out single-layer, non-medical masks completely.
Related: What’s the Difference Between N95 Masks and KN95 Masks?
“There are some cloth masks that have a filter you can put in a pouch. That’s functionally double-masking. So there are some masks that are, by themselves, acceptable,” says Cohen. These well-fitting cloth masks may even achieve filtration close to an N95, agrees Prickett, “especially if combined with a particulate filter.”
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N95 masks had been in short supply earlier on in the pandemic, with the CDC recommending that they should be reserved for the hospital and frontline workers who needed them the most. But supply chains and mask production have since normalized, so N95s, and their comparable counterpart KN95s, are now available to the public online. That being said, even the best N95 and KN95 masks are only effective when worn once or twice, and can’t be washed or reused. So if you’re looking to produce comparable results to medical-grade PPE, but want to feel a little more protected than just wearing a surgical or cloth mask by itself, double layering up might be your next best option.
Is Double-Masking Effective Against Covid?
According to a recent study, double-masking can produce 70-90 percent efficacy when it comes to filtering particles that can cause Covid-19, as opposed to around 50 percent efficacy from just wearing a surgical mask or non-medical cloth mask alone. While N95s are 95 percent effective at filtering 0.3-μm particles — which are smaller than droplets created when talking, coughing, or sneezing — the study found that the particles most likely to get through a mask to your respiratory system are around 2-μm in size. But one of the most important factors for successful protection reported? The fit of the mask itself.
“One of the arguments for double-masking is that when we use a [surgical] earloop mask, they don’t fit exactly right,” says Cohen. “Double-masking is a way of trying to turn your regular mask into more of an N95-type situation—where it’s tighter, where you’ve added an extra layer, where the virus droplets have to do a lot more dancing to get through. So it protects both you and the people that you’re with.”
Wearing a surgical earloop mask with a cloth mask on top seals the other mask down against your face, leaving less gaps for particles to get through, says Cohen. “For everyone who wears [surgical] earloop masks, if you’re like me and you wear glasses, they fog up and you can’t see anything, right? So you know that it’s not sealing properly. But when you put on a tightly-fitting N95, you know that it is.”
But the order in which you layer up your masks, and which masks you chose, are equally as important. “One of the things we see in hospitals is people use an N95, and then put another mask over the top of that, which doesn’t make any sense to me,” he says. “But a [surgical] earloop mask with a cloth mask on top does tighten the seal, because cloth masks tend to have a little tighter fit.”
Who Should be Double-Masking?
So when should you actually take the precaution to double mask? One factor to consider is whether or not you’re a part of a demographic that’s more vulnerable to contracting Covid-19, says Prickett. “Higher risk populations including those with immunocompromised conditions or their household members may want to consider double masking when out in public to further reduce exposure given newer viral variants.”
But what about the rest of the general population? Prickett says you should still consider double-masking in situations where there’s an unavoidably high risk of exposure. “Double masking may be a consideration when around a large group or when social distancing is not possible. These would also include known exposures to Covid-positive persons, or prolonged indoor events, especially with higher occupancy.”
Cohen says that frontline workers should think about double-masking because of increased time spent with the public, despite other precautions being taken. “A lot of frontline workers now have plexiglass between them and the customers they’re working with. But you can’t do that in a warehouse or in some other industries where you’re constantly moving back and forth, so it might make more sense for them to double-mask.”
Double-masking can also provide a certain degree of comfort, adds Cohen, considering heightened public concern since the presence of more-transmissible strains of Covid-19 have been located in the United States. “Double-masking is coming up more frequently in conversations now because some of the new viral variants seem to be a little more contagious, so there would be less variants necessary in order to cause infection.”
However, Prickett points out that these new variants have not yet changed the recommendations for masking in the general population. But their identification demonstrates the importance of wearing masks effectively and consistently. “They certainly highlight the importance of filtration and quality of masks in reducing spread.”
What Is the Best Way to Double-Mask?
Not all masks are created equal, says Prickett, and there are several important factors to consider when it comes to the effectiveness of your masks. This includes types of materials used, preferably two or three layers, proper fit and consistent use. “Studies have shown that well-fitting cotton masks, especially those with a cone shape may provide similar protection compared to medical grade surgical masks,” she says. “The best options are probably a tighter fitting cloth mask over a disposable surgical mask that will serve as an additional filter.”
1. Use a Disposable Mask As Your Bottom Layer
Starting with the disposable masks, you still want to make sure that the mask is made out of materials that will prevent the spread of respiratory particles. According to John Hopkins Medicine, though they aren’t tight-fitted, blue surgical masks can provide some protection from larger respiratory droplets, such as coughs and sneezes, because they’re fluid-resistant. They can also help prevent you from spreading infectious droplets to others.
Because there are so many varieties on the market, with varying numbers of layers and levels of filtration, make sure that your disposable mask at least comes with a hydrophobic (water-resistant) layer, and a non-woven layer made of polypropylene, which helps trap airborne particles. Some companies, such as Evolvetogether, have created disposable masks with higher levels of filtration, and are made in an FDA-registered PPE factory.
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You can also test the filtration of your masks by subjecting them to a light test—hold your mask up to a bright light source, like the sun, or shine your phone’s flashlight through the mask. The more light that passes through, the worse your mask’s filtration levels might be. Bill Nye also popularized a candle-blowing test on TikTok, showing that if you can easily blow out a flame from one foot away while wearing a mask, there’s not much in the mask that’s blocking your breath — and the viral particles within — from others.
2. Add a Cloth Mask Over Your Surgical Mask
For cloth masks, make sure you’re going for a breathable and protective material—we recommend a thick, tightly-woven cotton mask with multiple layers. Always check the label of your mask, too, as many on the market are now made of custom fabric blends. If your cloth mask doesn’t have adjustable straps, it should still be form-fitting enough that it won’t slip around when you’re wearing one. The best cloth face coverings are also ones that can be machine-washed, or washed by hand, and worn dozens of times. One of our most well-reviewed, lightweight cloth masks is from Everlane, which has a CDC-approved double layer design.
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3. Adjust the Fit to Form a Tight Seal
You can also enhance the fit while double masking by making adjustments to any masks you already have. The CDC recommends that the best face mask is one that “fits closely over your nose or one that has a nose wire to limit fogging.” You can use flexible metal strips, which help the top of a mask fit more securely over the nose bridge, or mask extenders, that customize how tight your mask sits on your face without relying on ear straps alone. If you’re still worried about fogging up in the winter cold, try looking for face masks specifically for glasses wearers.
While the seal of the mask is the biggest issue, the quality of the masks matter too. Face shields and acrylic-based masks alone are not completely effective at filtering germs and bacteria, and some types are not recommended if you’re looking for a higher level of protection. “I still see people wearing masks that have the exhalation valve,” says Cohen, “which provides zero protection, based on the fact that it shoots a jet of respiratory droplets out at the other person.”
Masks should also never restrict your breathing, especially while doubling up. Prickett says that patients with underlying respiratory issues may find it more difficult to breath with multiple masks on. “Weather may also play a role as double masking in hot and humid temperatures may be more difficult to wear consistently,” she says. “Trying to put on or take off an additional mask may be difficult for children or those with dexterity issues.” But that’s not an excuse to go completely maskless—in this case, a single well-fitting, high-quality mask should be used.
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While no mask is 100 percent perfect for double-masking, Cohen says that there’s data showing that masking can make the difference in effectively preventing community spread of disease. “We already have data from environmental physicists doing mask studies that can demonstrate evidence that double-masking is beneficial in a laboratory setting, that we haven’t see translated in social settings yet,” he shares. “The one thing we do know is that there is a lot of data, epidemiologically, that masks have done a lot for controlling the spread. So even a less-than-perfect [surgical] mask or cloth mask is still providing some benefit, particularly if multiple people are masked.”