Double-Masking: How Two Masks Block Covid-19 Coronavirus Better Than One

Wearing two things is not always better than wearing one.

Two neckties? That could be kind of odd for a job interview.

Two pairs of shoes? Perhaps if you are goat, not the greatest of all time but an actual goat.

Two pairs of Bernie Sanders mittens? That could make it tougher to grasp some things, like why doesn’t everyone have health insurance?

Two pairs of underwear? It totally depends on what kind of message you want to send to whom.

So how about wearing two face masks then? That’s one on top of another and not one over your mouth and nose and the other over your eyes.

Well, let’s take a look at how face masks work. First of all, wearing something is better than wearing nothing, which is a good general rule, even when you aren’t talking about face masks. Without anything covering your nose and mouth, you could be spewing out virus-laded particles into the air with every breath you take, especially if you are singing the song “Tub Thumping.” Because while you may be sexy and know it, you could be infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) without knowing it. A single face mask can block this spew and decrease the amount of virus that reaches the air.

Wearing a face mask may also protect you as well. It could provide some barrier to entry, blocking at least some viruses from getting into your nose and mouth. A cloth face covering or a surgical mask is not going to protect you as well as an N95 mask. But again, something is better than nothing. So wearing a face covering is nice for everyone around you and possibly you too. But can two masks be twice as nice?

In theory, a virus should have a tougher time getting through two layers than just one layer. In a commentary in the journal Med, Monica Gandhi, MD, MPH, a Professor of Medicine at the University of California, San Francisco (UCSF), and Linsey C. Marr, PhD, the Charles P. Lunsford Professor of Civil and Environmental Engineering at Virginia Tech, recommended wearing at least a “high-quality surgical mask or a fabric mask of at least two layers with high thread count.” But they added that wearing a cloth mask tightly on top of a surgical mask could provide even more protection. Anthony Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases (NIAID) favors double-masking too. As you can see this segment from the Today show, Fauci said, “If you have a physical covering with one layer, you put another layer on, it just makes common sense that it likely would be more effective”:

If two layers are better than one layer, how about three layers? Gandhi and Marr did mention a three-layer mask as a possibility for extra protection. Such a mask could have two outer layers made out of a flexible, tightly woven fabric that can conform to your face and sandwich a middle layer. The middle layer shouldn’t be a creamy, high fructose corn syrup and soy lecithin filling. You are providing a barrier to your nose and mouth, not making an Oreo cookie. Instead, the middle layer should be something like vacuum bag material that can filter out small particles.

If three is better than two, how about four? Or five? Or 271 face masks? Well, at some point, too many face masks could become too heavy and make you topple over like Toucan Sam wearing high heels.

Plus, there is the whole breathing thing. One face mask probably won’t really impair your breathing. Neither will two face masks, depending on the material. However, adding more and more mask layers may eventually make it tougher to exchange air, assuming that you are not a ficus plant. The optimal number of face masks is a balance between filtering and breathing and depends on the structure and material of the mask. Naturally, a face mask made out of concrete is going to be tougher to breathe through than one out of a porous cloth.

The other issue is fit. Make sure that at least one of the face masks that you wear fits snugly on your face. It should not leave gaps between your face and the mask that allow viruses to drive little trucks through them. A second mask can actually help the mask closest to your face fit more snugly. Like Edward hugging Bella on the Twilight series, the outer mask can push the inner mask closer to your face. But as is the case with marmots in your bedroom, more masks is not necessarily better. Sometimes additional face masks can actually pull other face masks off your face. Therefore, as they say on the London subway, mind the gap. And for Pete’s sake, keep the mask over both your mouth and your nose. Consider a face mask to be underwear for your face, and don’t let anything stick out so to speak.

Some have suggested that two non-N95 masks can get close to the protection offered by one N95 mask. This may be some premature speculation though. After all, N95 masks tend to have other mechanisms that can prevent viruses from getting through, such as interlacing fibers that create rather tortuous paths and an electrical charge that may cause small particles to stick to the fibers.

All told, double masking in most cases will provide more protection than single-masking. That’s protection for others and potentially for you. This can be true even when the inner mask is an N95 one. N95 masks aren’t perfect and could benefit from extra protection. Moreover, an outer covering can keep the N95 mask from getting dirty and wet. And in this situation, dirty and wet is not good.