Wearing a mask is essential during the COVID-19 pandemic. It will help prevent both you and others from getting COVID-19. This is more important than ever with new, more easily transmitted variants of COVID-19 on the rise.
CDPH has issued Guidance on the Use of Face Coverings to align with CDC
recommendations. Consistent and correct mask use by people who are not fully
vaccinated is especially important indoors.
Poor Fitting Face Covering
An effective mask has both good fit and good filtration. A well fitted mask has no gaps between the face and mask, such as above the nose or at the sides. With gaps, air that has virus particles can easily leak in or out around the sides of the mask. Good fit forces the air that you breathe out and breathe in to go through the mask and be filtered. Good filtration blocks the virus particles from going through the mask itself. You can get good filtration with the right materials and by using more layers.
Good fit and filtration improve protection for others if you are infected and protection for you if you are exposed to an infected person.
"Double masking" is an effective way to improve fit and filtration. A close-fitting cloth mask can be worn on top of a surgical/disposable mask to improve the seal of the mask to the face. Layering more than two masks is not recommended as this could be difficult to breathe through. Also, it is not recommended to wear two medical masks, or to wear a medical mask on top of a KN95 or an N95. Double masking may be appropriate where improved fit and filtration are especially important, and some situations where this may be considered are listed below.
Regardless of the mask type, it is only effective if it is worn over your mouth and nose.
When Wearing an Effective Mask is Especially Important
Some situations require a higher level of protection (improved fit and/or improved filtration):
In indoor settings with unvaccinated persons or with persons whose vaccination status is unknown.
In close quarters with other people where social distancing is not possible (examples: riding a crowded bus, waiting in line at a crowded airport terminal).
In any public place for people who are older or with medical conditions that put them at higher risk of severe COVID illness.
Even when you're at home, there are times when a higher level of protection is important, such as when:
- Providing care for family members who are sick with or may have been exposed to someone with COVID-19.
- Living in a household with someone who is suspected of having or has COVID-19.
- Someone from outside your household comes into your home (example: friend, relative, repair person).
- You work outside the home and live with someone who is older or with a medical condition that puts them at higher risk of severe COVID illness.
As noted in the CDC's Frequently Asked Questions about COVID-19 Vaccination, it is important to continue to wear a mask even after receiving the COVID-19 vaccine to protect yourself and others. Experts are continuing to study whether getting a COVID-19 vaccine will prevent you from spreading the virus that causes COVID-19 to other people, even if you don't get sick yourself. It's important for everyone to continue using all the tools available to help stop this pandemic as we learn more about how COVID-19 vaccines work in real-world conditions.
Choosing your Mask
Cloth masks can work well if they are tight fitting and made of materials that filter out small particles. Good cloth masks have:
- Two layers of tightly woven cotton with a third layer of non-woven fabric. The third layer could be a mask filter insert, or a synthetic fabric such as polypropylene.
- Nose wires to reduce gaps from the nose.
- Adjustable ear loops or straps that go around the head to reduce gaps from the face.
Face coverings without these properties should not be used in higher risk situations if other options are available. Examples of less effective face coverings are two-layer cotton masks, bandanas, and gaiters.
Medical Masks (also called Surgical Masks or Disposable Face Masks)
Medical masks include various types of loose-fitting disposable masks. The fit of a medical mask can be improved with a simple modification or by using a mask brace. Look for the following when buying medical masks:
- Masks with three layers of non-woven material.
- An adjustable nose bridge.
- Surgical masks with ties may provide a closer fit than ear loops.
KN95s are a type of international respirator that have not gone through the same strict testing as N95 respirators. Respirators are designed to provide a specific level of protection. Testing of KN95s has shown that some models are not effective. For example, testing by the National Institute for Occupational Safety and Health (NIOSH) has shown that more than half of KN95s tested did not filter particles as well as the manufacturers claimed. If you do choose to use a KN95, we recommend finding a KN95 that has been tested by NIOSH and has a minimum "filtration efficiency" of 95% or higher.
When they fit well, N95 respirators are highly effective in preventing the spread of COVID-19. Make sure they are NIOSH-approved (have a TC-84A-XXXX number printed on the respirator). Choose a size and model that fits your face and has no gaps. Test it by doing a seal check to make sure it fits. As the availability of respirators increases, individuals may choose to wear them instead of other options, particularly in settings, such as those described above, where greater protection is needed.
If you wear an N95 respirator, you should not wear an additional face covering over or under the respirator, as it can interfere with the seal to the face.
- Cloth mask with 1 or 2 layers
- Fitted medical mask
- Cloth mask with 3 layers
- Double mask (Medical + Cloth)
CDC - Improve How Your Mask Protects You
CDC - Improve the Fit and Filtration of Your Mask to Reduce the Spread of COVID-19
Video Instruction to Improve Medical Mask Fit
CDC Study - Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure
NIOSH Testing of International Respirators
NIOSH-Approved Particulate Filtering Facepiece Respirators
How to Conduct a Seal Check of an N95