From the Centers for Disease Control and Prevention

• Improve fit to help prevent air (potentially with respiratory droplets containing the virus) from flowing freely around the edges of the mask and instead forcing air to flow through the mask.
• Improve filtration to cause more respiratory droplets containing the virus to be captured by the mask.

How to Improve Fit

COVID-19 spreads mainly from person to person through respiratory droplets that come out of the nose and mouth when people breathe, cough, sneeze, talk, shout, or sing. These respiratory droplets travel in the air and can then land in the noses and mouths of others, which spreads COVID-19. Therefore, in order to be effective, masks must always be worn over the nose and mouth.

Ensuring that masks fit well on the face is very important to help prevent getting and spreading COVID-19. A common problem with some masks is that there can sometimes be gaps between the mask and the mask wearer’s face. When there are gaps, air with respiratory droplets containing the virus can leak in and out around the edges of the mask (on the top or the sides). To help prevent air leakage, masks should fit snugly against the sides of the face and not have gaps.

Options to Improve Mask Fit

Nose Wires: Use cloth or medical procedure masks that have a nose wire (a metal strip along the top of the mask) to help prevent air leakage at the top of the mask. Nose wires can also help to prevent fogging of eyeglasses. To get a good fit, make sure to bend the nose wire over your nose to conform to your face.

Mask Fitters and Braces: These devices can be used over a medical procedure mask or a cloth mask to improve the fit by helping to reduce air leakage from around the edges of the mask.

Knotting and Tucking: This technique can be used to improve the fit of a medical procedure mask. Knot the ear loops of the mask where they join the edge of the mask, then fold and tuck the unneeded material under the edges. (For instructions, see the following video)

How to check mask fit

• Check for gaps by cupping your hands around the outside edges of the mask. Make sure no air is flowing from the area near your eyes or from the sides of the mask.
• If the mask has a good fit, you will feel warm air come through the front of the mask and may be able to see the mask material move in and out with each breath.

How to Improve Filtration

Another important step to increase the protection offered by your mask is to improve filtration. Masks capture respiratory droplets containing the virus when the wearer breathes out, blocking them from reaching the outside air and protecting others. They also serve as a barrier to protect the wearer by capturing respiratory droplets containing the virus breathed out by others, so that the wearer does not breathe them in. A mask with improved filtration will stop more respiratory droplets containing the virus from getting inside your mask if others are sick or escaping from your mask if you are sick.

Layering

Adding more layers of material to a mask (layering) is a good way to reduce the number of respiratory droplets containing the virus that come through the mask. One layering strategy is to use a cloth mask that has multiple layers of fabric. Another strategy is to wear two masks.

Improve Mask Fit and Filtration by Wearing Two Masks

Wearing a second mask on top of a first mask can

• Improve fit by pressing the inner mask closer to the face, thereby reducing the amount of air that leaks around the edges of the masks.
• Improve filtration by adding more layers of material to reduce the number of respiratory droplets containing the virus that come through the masks.

One way to do this is to wear a medical procedure mask underneath a cloth mask. A recent study conducted in a laboratory found that this combination provided much better protection to the wearer and to others as compared with a cloth mask by itself or a medical procedure mask by itself.

However, there are some mask combinations that should not be used

• Do not combine two medical procedure masks. Medical procedure masks are not designed to fit tightly and wearing a second medical procedure mask on top of the first medical procedure mask does not help to improve the fit.
• Do not combine a KN95 mask with any other masks. You should only use one KN95 mask at a time, and you should not use any type of second mask on top of or underneath a KN95 mask.