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The City of Cambridge issued an emergency order requiring that face masks or coverings be worn in indoor public places. The order takes effect at 8 a.m. on Friday, September 3, 2021.

It applies to everyone over the age 2, with exceptions in alignment with the Centers for Disease Control and Prevention and the Massachusetts Department of Public Health guidelines.  For more information, see the full City of Cambridge Emergency Order and the City's Masks and Face Coverings page.

Given the concerns about the highly contagious delta variant and the potential for fully vaccinated people to transmit the virus, the Cambridge Public Health Department also recommends that residents—regardless of vaccination status—wear a mask when outside the home.  
Wearing a mask in all indoor settings outside the home is especially important for individuals who are unvaccinated, as well as vaccinated people who:
  • Have or live with someone who has a weakened immune system.
  • Are at increased risk for severe disease because of age or an underlying medical condition or live with someone who is.
  • Live with someone who is unvaccinated.

The Centers for Disease Control and Prevention issued similar guidance in July 2021 for counties with substantial or high levels of COVID-19 transmission.

Choosing the Best Mask for You

Not all masks provide the same level of protection. New research shows that high quality “medical-style” masks available to the public are most effective at protecting the wearer from infection.

Look for masks that fit snugly and block at least 90% of small viral particles from being breathed in. Masks should also be comfortable, especially if they are being worn throughout the day. 


Wear a mask with excellent filtration. Aim for 90-95%.

  • Several types of disposable masks available to the public provide excellent personal protection. These “high filtration” masks include KF94 masks (made in Korea), KN95 masks (made in China) and flat medical-style masks that are quality-certified.
  • KN95 and KF94 fit more snugly, depending on face-shape, than flat medical-style masks. 
  • If shopping for masks, some keywords to look for are KF94, KN95, or ASTM-rated.
  • About Cloth Masks: Cloth masks are best suited to outdoor use when it's easy to social distance. Most cloth masks do a good job of protecting others if you are sick.

More information on pros and cons of different types of masks is available on the CDC website.


Choose masks that fit snugly and cover your nose, mouth, and chin.

  • All edges should touch your skin so that unfiltered air does not escape or enter through the gaps.
  • Try different shaped masks to fit your face.
  • Try "ear savers" or mask straps to change the way a mask fits on your face.
  • A bendable nose clip is important for keeping masks in place and closing gaps.
  • If you cannot get a good fit with a flat medical-style mask, consider placing a cloth mask over it. This is known as “double masking.”
  • See the CDC website for more tips on improving mask fit and double-masking
Mask Reuse and Care
  • High quality disposable masks can be reused many times, as long as they are not visibly damaged or soiled. In independent tests, these masks remained effective after 40 hours or more of use. 
  • Masks that have been filtering germs all day may have germs on their outside surface. When removing a mask, hold it by the ear loops and wash your hands afterwards.
  • Store used disposable masks in the open air or a paper bag to dry until you need them. 
  • Do not clean your disposable masks with soap or alcohol—or put them in the washing machine—because this will destroy their ability to block viral particles. Medical-style flat masks and KF94/KN95 masks still work when wet with perspiration. They can be dried with a tissue. 
  • Bacteria and fungi can grow on cloth masks, so they need to be washed daily with your laundry or in hot soapy water in the sink.
Updated August 27, 2021



Cambridge Public Health Department
119 Windsor Street
Cambridge, MA 02139
617-665-3826 (main)
617-665-3800 (main)
617-665-3888 (fax)
617-643-0744 (TTY)

Hours: Monday-Friday:
8:30 a.m.–5 p.m.
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Susan D. Breen
Interim Chief Public Health Officer



Cambirdge Health Alliance

Cambridge City
City of Cambridge