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Updated on November 11, 2020 to reflect the latest .

Wearing masks is all about stemming the person-to-person respiratory droplets that contain the infectious virus that causes COVID-19--a form of “source control,” explains �鶹��ý�����’s David P. Calfee, MD, MS, chief hospital epidemiologist for NewYork-Presbyterian/Weill Cornell Medical Center.

“Wearing a mask reduces the risk that we will transmit the SARS-Co-V-2 virus to others and reduce the amount of virus that we shed into the air,” he says, even if the precise degree to which we can reduce it has not yet been definitively established. also has strengthened its language on mask wearing to acknowledge that masks also protect those who wear them.

“Studies demonstrate that cloth mask materials can also reduce wearers’ exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns,” the CDC statement says.

Here Dr. Calfee shares his guidance and knowledge on mask wearing.

Which are the most effective masks to wear for those who are not in the medical field and are not frontline workers?

For general use in the community, one can wear a surgical mask, or a cloth face mask or face covering. (N95 masks should be reserved for healthcare workers and other first responders.)

There also are some types of masks that are not recommended. Those with exhalation valves may allow more respiratory droplets and viral particles into the air, compared with those without the valves.

Gaiters and bandanas have not been well studied, but because they don’t fit as loosely to the face, may be less effective in blocking droplets and preventing transmission. Similarly, we don’t know how effective it is to wear plastic face shields worn by themselves, so they should not be considered an alternative to wearing masks. If you’re going to wear a face shield, you should wear it in addition to wearing a mask.

Masks now are easily available for purchase, but some people prefer to make their own masks. What is the best material to use?

Cloth masks should be made of two layers of breathable, washable fabric. (Vinyl and plastic should not be used because they impede breathing.)

The Centers for Disease Control and Prevention provides helpful information for those who want to make their own cloth masks.

Is it safe for children to wear masks?

Yes (although mask use is not recommended for children under two years old because of the risk of suffocation).

Children who have returned to school in person may sometimes need “mask breaks.” Ideally, that should occur when students are social distancing and are six feet from one another, and outside, where there is greater ventilation.

Who should not wear a mask?

In addition to children under two years old, people who are unconscious, incapacitated, or otherwise unable to remove a mask without assistance, should not wear masks.

For people who fall into this category, social distancing remains very important. They should avoid crowds, particularly indoors, and forgo settings in which others are not wearing masks.

How should a mask fit? Is it okay to use cord adjusters?

The mask should fit snugly over both the mouth and the nose, without large gaps between the mask and the face. If someone needs to use a cord adjuster—or devices to reduce the pressure of ear loops on one’s ears—be sure the mask still fits snugly over the mouth and nose.

What is the best way to put on and remove masks?

Masks should be touched with clean hands, so perform hand hygiene before putting on or removing a mask.

When we must handle masks, it’s best to touch only the ties or ear loops to avoid touching the surfaces of the mask itself. And when we fold a mask to put it away, it’s important to do so in a way that avoids contamination of the mask by the environment, and the environment by the mask. So the part of the mask that touches your face should be folded inward so it doesn’t have contact with your hands or surfaces.

How should we care for cloth masks?

We should regularly wash cloth and reusable masks with laundry detergent on a high heat setting, and masks should be completely dry before wearing them again.