Your Guide to Masks
- Everyone 2 years of age or older who is not fully vaccinated should wear a mask in indoor public places.
- In general, you do not need to wear a mask in outdoor settings.
- In areas with high numbers of COVID-19 cases, consider wearing a mask in crowded outdoor settings and for activities with close contact with others who are not fully vaccined.
- People who have a condition or are taking medications that weaken their immune system may not be fully protected even if they are fully vaccinated. They should continue to take all precautions recommended for unvaccinated people, including wearing a well-fitted mask, until advised otherwise by their healthcare provider.
- If you are fully vaccinated, to maximize protection from the Delta variant and prevent possible spreading to others, wear a mask indoors in public if you are in an area of substantial or high transmission.
- If you are fully vaccined, see ‘When You’ve Been Fully Vaccinated‘.
Wearing a mask over your nose and mouth is required on planes, buses, trains, and other forms of public transportation traveling into, within, or out of the United States and while indoors at US transportation hubs such as airports and train stations. Travelers are not required to wear a mask in outdoor areas of a conveyance (like on open deck areas of a ferry or the uncovered top deck of a bus.)
How to Select
Mask Use & Carbon Dioxide
- Wearing a mask does not raise the carbon dioxide (CO2) level in the air you breathe.
- Cloth masks and surgical masks do not provide an airtight fit across the face. CO2 escapes into the air through the mask when you breathe out or talk. CO2 molecules are small enough to easily pass through mask material. In contrast, the respiratory droplets that carry the virus that causes COVID-19 are much larger than CO2, so they cannot pass as easily through a properly designed and properly worn mask.