Can face masks help slow the spread of the coronavirus (SARS-CoV-2) that causes COVID-19? Yes. Face masks combined with other preventive measures, such as getting vaccinated, frequent hand-washing and physical distancing, can help slow the spread of the virus.

The U.S. Centers for Disease Control and Prevention (CDC) recommends fabric masks for the general public. If you’re fully vaccinated and are in an area with a high number of new COVID-19 cases, the CDC recommends wearing a mask indoors in public and outdoors in crowded areas or when you are in close contact with unvaccinated people. People who haven’t been fully vaccinated should wear face disposable masks indoors and outdoors where there is a high risk of COVID-19 transmission, such as crowded events or large gatherings. The CDC says that surgical N95 masks should be reserved for health care providers. Respirators such as KN95s and non-surgical N95s can be used by the general public when supplies are available.

The World Health Organization (WHO) recommends medical masks for health care workers as well as for anyone who has or may have COVID-19 or who is caring for someone who has or may have COVID-19.

How do the different types of masks work?

Medical masks

Also called surgical masks, these are loosefitting disposable masks. They're meant to protect the wearer from contact with droplets and sprays that may contain germs. A 3ply medical disposable mask also filters out large particles in the air when the wearer breathes in.

To make medical masks more form-fitting, knot the ear loops where they attach to the mask. Then fold and tuck the unneeded material under the edges.

N95 masks

An N95 mask is a type of respirator. It offers more protection than a medical mask does because it filters out both large and small particles when the wearer inhales. Non-surgical N95s can be used by the general public when supplies are available.

The CDC has said surgical N95 masks should be reserved for health care providers. Health care providers must be trained and pass a fit test before using a surgical N95 mask. Like surgical masks, N95 masks are intended to be disposable. However, researchers are testing ways to disinfect and reuse them.

Some N95 masks, and even some cloth masks, have valves that make them easier to breathe through. Unfortunately, these anti-dusk masks don't filter the air the wearer breathes out. For this reason, they've been banned in some places.

Cloth masks

A cloth mask is intended to trap respiratory droplets that are released when the wearer talks, coughs or sneezes. It also acts as a barrier to protect the wearer from inhaling droplets released by others.

The most effective cloths masks are made of multiple layers of tightly woven fabric like cotton. A mask with layers will stop more droplets from getting through your mask or escaping from it.

How to get the most from your mask

The effectiveness of cloth and medical masks can be improved by ensuring that the masks are well fitted to the contours of your face to prevent leakage of air around the masks' edges.

Masks should be snug over the nose, mouth and chin, with no gaps. You should feel warm air coming through the front of the mask when you breathe out. You shouldn't feel air coming out under the edges of the mask.

Masks that have a bendable nose strip help prevent air from leaking out of the top of the mask.

Some people choose to wear a disposable mask under their cloth mask. In that case, the cloth mask should press the edges of the disposable mask against the face. Don't add layers if they make it hard to breathe or obstruct your vision.

Proper use, storage and cleaning of masks also affects how well they protect you. Follow these steps for putting on and taking off your mask or disposable glove:

Wash or sanitize your hands before and after putting on your mask.

Place your mask over your mouth and nose and chin.

Tie it behind your head or use ear loops. Make sure it's snug.

Don't touch your mask while wearing it.

If you accidentally touch your mask, wash or sanitize your hands.

If your mask becomes wet or dirty, switch to a clean one. Put the used mask in a sealable bag until you can get rid of it or wash it.

Remove the mask by untying it or lifting off the ear loops without touching the front of the mask or your face.

Wash your hands immediately after removing your mask and protective garment.

Regularly wash cloth masks in the washing machine or by hand. (They can be washed along with other laundry.)

And don't forget these precautions:

Don't put masks on anyone who has trouble breathing or is unconscious or otherwise unable to remove the mask without help.

Don't put masks on children under 2 years of age.

Don't use face masks as a substitute for physical distancing.

What about face shields?

The CDC doesn't recommend using face shields instead of masks because it's unclear how much protection shields provide. However, wearing a face mask may not be possible in every situation. If you must use a face shield instead of a mask, choose one that wraps around the sides of your face and extends below your chin.

Do you still need to wear a facemask after you’re fully vaccinated?

After you are fully vaccinated, you can more safely return to doing activities that you might not have been able to do because of the pandemic. However, if you are in an area with a high number of new COVID-19 cases, the CDC recommends wearing a mask indoors in public and outdoors in crowded areas or when you are in close contact with unvaccinated people. You're considered fully vaccinated 2 weeks after you get a second dose of an mRNA COVID-19 vaccine or 2 weeks after you get a single dose of the Janssen/Johnson & Johnson COVID-19 vaccine.

In the U.S., everyone also needs to wear a mask while on planes, buses, trains and other forms of public transportation.