On February 10, the Centers for Disease Control and Prevention (CDC) released new masking guidance to help reduce the spread of Covid-19. Universal masking has already been widely recommended by public health authorities globally, including the World Health Organization (WHO). So if one mask is good, is two better?

The CDC conducted experiments to find ways of improving the fit of  non-respirator masks such as cloth masks, surgical masks, and other non N-95 varieties, to maximize their effectiveness. The finding: If you want to reduce exposure, fit a cloth mask over a medical procedure mask (surgical mask). According to lab tests by the CDC, this can help decrease exposure to potentially infectious aerosols by up to 95 percent.

Wearing a single mask is not effective if air is going around it and not through it, says Dr. Bruce Hirsch, an infectious disease doctor at Northwell Health. But if you only have a surgical mask, you can make it more effective by knotting the ear loops and then tucking in and flattening the extra material close to the face to get a tighter fit. 

Both methods substantially reduce your exposure to the aerosol droplets that cause Covid-19. Dr. Hirsch notes that you shouldn't go overboard and wear more than two masks at a time, however. Three is not better than two. If the air resistance through the mask becomes too great, it's more likely you'll lose the tight fit around the mask, which is crucial. 

Of course, you also don't want the mask to be uncomfortable. "The most important mask is the one you're going to wear all the time when you're in high-risk situations," says Dr. Bob Bollinger, a professor of infectious diseases at the Johns Hopkins University School of Medicine and inventor of Emocha Health, a medtech company that helps patients adhere to medication. "There's no point in wearing masks if you're not going to use them consistently."

Keep in mind that masks are only one part of a much larger picture. While masks are great, they're not sufficient. Neither is a vaccine or social distancing, taken separately. "All the layers of protection that we have are imperfect," says Dr. Hirsch. "It's all hands on deck, and everything that we can do to look at different interventions and to try to make each intervention more effective can add up to a cumulative power to eliminate this epidemic."

An unsafe workplace can hinder any company's ability to operate at maximum output. Yet as of February 1, only 14 states and the District of Columbia have universal mask mandates. Without a state mandate there's even more of a burden on business organizations to have their own mandatory mask policies. But even with a state mandate, employers should take on the task of educating employees on the proper use and effectiveness of wearing masks and keep them up to date on the proper use and effectiveness of all PPE equipment.

On a broader note, Dr. Christine Crawford, an epidemiologist who previously worked for the Epidemic Intelligence Service, a program of the CDC, says these latest guidelines, as well as a new focus on guidelines for schools, may mark a shift in how the CDC is operating under the Biden administration. "This the beginning of them being empowered and resourced," she says. "There's a reason that the CDC has been the gold standard for disease control for years. Now they can do what they do."