How well do face masks protect against COVID-19?

Can face masks help slow the spread of the virus that causes coronavirus disease 2019 (COVID-19)?

Yes. When used with measures such as getting vaccinated, hand-washing and physical distancing, wearing a face mask slows how quickly the virus that causes COVID-19 spreads.

The U.S. Centers for Disease Control and Prevention (CDC) recommends wearing masks if you choose to, and in specific places and situations.

In areas that have many people with COVID-19 in the hospital, the CDC recommends wearing a face mask indoors in public.

The CDC says that you should wear the most protective mask that you'll wear regularly, fits well and is comfortable.

Respirators such as nonsurgical N95s give the most protection. KN95s and medical masks provide the next highest level of protection. Cloth masks provide less protection. The CDC says that surgical N95 masks should be reserved for health care professionals.

Masking suggestions are a bit different for people at higher risk of serious illness. This includes people with risk factors such as older age. It also includes people with weakened immune systems and those who live with or care for someone with these risk factors.

For people at high risk, the CDC suggests you wear a mask that provides you with the most protection possible. Wear a mask while in public indoor spaces when your area has a high number of people with COVID-19 in the hospital.

Check with your doctor to talk about when to wear a mask at other times.

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 medical 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 loose material under the edges.

Wearing a medical mask doesn't increase the level of carbon dioxide in the air you breathe.

KN95 masks

A KN95 mask is a type of respirator that meets certain international standards. It offers more protection than a medical mask does because it filters out both large and small particles when the wearer inhales. But be cautious when buying a KN95. Some may not meet the quality standards, so consider researching the source carefully.

N95 masks

An N95 mask is a type of respirator that meets U.S. quality standards. An N95 offers the highest level of protection. It offers more protection than a medical mask does because it filters out both large and small particles when the wearer inhales. Nonsurgical N95s can be used by the general public.

The CDC has said surgical N95 masks should be reserved for health care professionals. Like surgical masks, N95 masks are intended to be disposable. But researchers are testing ways to disinfect and reuse them.

To work best, N95 masks should fit your face tightly.

Some N95 masks, and even some cloth masks, have valves that make them easier to breathe through. But these 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 released when the wearer talks, coughs or sneezes. It also acts as a barrier to protect the wearer from breathing in droplets released by others.

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

Wearing a mask doesn't increase the level of carbon dioxide in the air you breathe.

How to get the most from your mask

Your mask works best if it fits your face closely and has no gaps around the edges. This helps air and breath move through the mask, not around the edges.

You should feel warm air going out the front of the mask when you breathe out. You shouldn't feel your breath coming out under the edges of the mask.

Use masks that have bendable nose strips, as these help prevent air from leaking out of the top of the mask.

Layers of material offer more protection.

Some people choose to wear a medical mask under a cloth mask. In that case, the cloth mask should press the edges of the medical mask against the face. Don't add layers if they make it hard to breathe or block your vision. And don't use another mask with a KN95 or N95 mask.

If you wear a KN95 or N95 mask, make sure it fits and seals close to your face.

A child's mask should be specifically made for children in order to fit properly. Make sure it fits close over the nose, mouth and chin.

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:

• 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 tight against your face.
• 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. Fold the outside corners together.
• Wash your hands immediately after removing your mask.
• Regularly wash cloth masks in the washing machine or by hand. (They can be washed along with other laundry.) Dry them in the dryer or hang them outside in the sun.
• Throw away disposable masks after wearing them once.

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 age 2.
• Don't use face masks instead of physical distancing.

What about face shields?

Experts do not recommend using face shields instead of masks. It's not clear how much protection shields provide. But 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 face mask after you're vaccinated?

After getting vaccinated, you can more safely return to doing activities that you might not have been able to do because of high numbers of people with COVID-19 in your area. However, if you are in an area with a high number of people with COVID-19 in the hospital, the CDC recommends wearing a mask indoors in public. You are considered up to date with your vaccines if you have gotten all recommended COVID-19 vaccine shots when you become eligible.