Updated March 26, 2021. 



Viruses cannot replicate outside of a host cell. The virus that causes COVID-19 can live on common surfaces such as paper, fabric or metal for varying periods of time, measured in hours to about a week. Importantly, however, the virus cannot replicate or reproduce on these surfaces. A face mask, for example, does not serve as an “incubator” for the virus.

People can become infected by the transmission of coronavirus via the eyes, nose and mouth. Reducing the tendency to touch one’s face and eyes is a possible benefit of face coverings.


Portsmouth has a Mask Ordinance in effect through June 30, 2021. Mask Ordinance FAQs.

NH has a Mask Mandate effective statewide through April 15, 2021.

President's Executive Order (January 20, 2021) on mask wearing in Federal buildings and on interstate transportation. Affirming the Executive Order, the CDC has issued an order  (effective February 1, 2021) requiring travelers to wear a mask on public transportation in the U.S. The CDC order states passengers on airplanes, trains, buses, subways, ships, ferries, taxis and ride-shares must wear a mask that covers their nose and mouth while getting on such vehicles, during the ride and while getting off.

According to the Centers for Disease Control and Prevention (CDC), individuals should wear face masks in public, whenever possible, to prevent the spread of COVID-19.

  • The CDC does not limit this suggestion based solely on location (indoors or outdoors). Nor is the recommendation limited to use in situations when physical distancing is not possible although it is “especially” important in those situations. Note that physical distancing per the CDC is not simply 6 feet, but “at least 6 feet..
  • The effectiveness of this approach in the prevention of COVID-19 spread depends on the widespread use of the mask By simply wearing a mask, you reduce your own risk and help to protect everyone else, especially the most vulnerable among us.
  • Broad use of face masks in public and when congregating with people outside of one’s household is particularly important given the ability of asymptomatic carriers to infect others. Exceptions are made for children under the age of 2 years (CDC recommendation) and for certain medical conditions. Note: Portsmouth ordinance sets the age limit at 6.

What is a mask?

For the purposes of this document, a “mask” is a product, either commercially manufactured or individually constructed, that covers a person’s nose and mouth, and is intended to provide a barrier to the transmission of the virus that causes COVID-19. Masks are sometimes referred to as “face masks” or “face coverings.”

Why are masks important during the COVID-19 pandemic?

The widespread and appropriate use of masks is one strategy to reduce the risk of viral spread. Expert medical and scientific opinion, backed by a wealth of research, strongly supports the use of masks to improve public health and safety.  Early in the pandemic, it was thought that wearing a mask would protect others, but protection of the wearer was uncertain. However, recent demonstrates that masks do protect and reduce risk for the person wearing a mask as well as others.

What should I look for in a mask?

According to the CDC and expert opinion, an effective mask:

  • Has 2-3 layers of tightly woven, washable, breathable fabric
  • Completely covers the nose and mouth
  • Fits snugly with minimal gaps (“face-hugging” fitted shapes have less gapping). A new technique called "knot and tuck" makes adjusts the fit of disposable masks to offer a better fit. 


  • Masks with exhalation valves or vents as these will allow the virus to escape
  • Thin or loosely- woven fabrics (if you can see light through the mask, it is probably inadequate)
  • Scarves, ski masks, and single layer gaiters or balaclavas are not substitutes for masks, but may be worn OVER an adequate face mask for warmth.

How should a mask be worn?

  • With clean hands, put the mask over your nose and mouth and secure it under your chin.
  • Fit the mask snugly against the sides of your face, secure the loops over your ears or tie the strings behind your head, and pinch the nose clip (if the mask has one). The properly fitting mask should fit snugly and not slip down easily.

Further handling of the mask (adjusting, pulling down, etc.) should be minimized and done with clean hands. 

Keep a spare mask on hand. Change your mask if it becomes wet. A wet mask is harder to breathe through, is less efficient at filtering, and vents more around the edges of the mask.

Place any used wet or dirty masks in a plastic bag to avoid contamination of other surfaces with the virus. Wash cloth masks frequently. Throw away disposable masks after using.

What can I do to make wearing a mask even more effective, without using supplies like N95 masks that should be saved for front line workers?

Double-masking: In a January 2021 interview, Dr. Fauci recommended the wearing of two masks as simple common sense: if one layer filters out respiratory droplets that could contain COVID-19, two layers filter out even more. In the same article, an infectious disease expert and an engineer reported research showing that wearing a surgical mask underneath a cloth mask provides maximal protection, because the surgical mask acts as a filter and the cloth adds an additional layer and helps with fit.

Cloth Masks: The CDC recommends that people wear masks that have at least two layers of tightly woven cotton fabric, such as quilting fabric or cotton sheets. CDC also notes that silk (from which many commercial masks are made) is more resistant to moisture than cotton. 

  • Cloth masks with pockets that can be filled with filter material such as polypropylene offer additional protection. A polypropylene filter can create static electricity that enhances the capture of particles in respiratory droplets. Polypropylene can be found at many home goods and crafts stores.

Disposable masks: Because disposable surgical masks made from a plastic-derived material called polypropylene have been shown to be more effective at filtering particles than just a cloth mask, the wearing of a disposable mask under a cloth mask is more effective than just two cloth masks, or a double-layer cloth mask. The CDC says not to use double disposable masks, and not to combine a KN95 mask with any other mask.

N95 Masks: N95 respirators are face masks that are designed to fit very close to the face, forming a seal that filters 95% of airborne particles. These masks are not recommended for the general public, because they should be reserved for healthcare workers and medical first responders.

KN95 Masks: Consider a carefully sourced KN95 mask. According to medical experts as reported by Healthline, a KN95 mask can filter 95 percent of aerosol particles similar to the N95. Both masks are made from several synthetic material layers but only the N95 has been approved by the National Institute for Occupational Safety and Health (NIOSH). However, one review found that nearly 70 percent of the KN95s produced in China did not meet the NIOSH filtering requirements, so buying from a reputable source is critical.

A mask alone does not provide perfect protection. Use masks along with other strategies such as physical distancing, frequent hand-sanitizing and avoiding gathering in poorly-ventilated spaces.

A CDC report (February 10, 2021) added to information about the effectiveness of different mask behaviors.

What is already known about this topic?

Universal masking is recommended to slow the spread of COVID-19. Cloth masks and medical procedure masks substantially reduce exposure from infected wearers (source control) and reduce exposure of uninfected wearers (wearer exposure).

What does the report say?

CDC conducted experiments to assess two ways of improving the fit of medical procedure masks: fitting a cloth mask over a medical procedure mask, and knotting the ear loops of a medical procedure mask and then tucking in and flattening the extra material close to the face. Each modification substantially improved source control and reduced wearer exposure. 

Mask Effectiveness study

What are the implications for public health?

These experiments highlight the importance of good fit to maximize mask performance. There are multiple simple ways to achieve better fit of masks to more effectively slow the spread of COVID-19.

The Centers for Disease Control and Prevention (CDC) suggest that the general public not use products intended for healthcare workers, such as N95 respirators (details below), as this could lead to shortages of equipment where most needed.

Can the coronavirus grow on the mask?

No. Viruses cannot replicate outside of a host cell. The virus that causes COVID-19 can live on common surfaces such as paper, fabric or metal for varying periods of time, measured in hours to about a week. Importantly, however, the virus cannot replicate or reproduce on these surfaces. A face mask cannot and does not serve as an “incubator” for the virus.


What about face shields? How are they different from masks?

There is little to no research as yet on the use of face shields in community settings. Most are open below the chin, which can allow the virus to spread outside of the shield.  If used, wear the face shield over a mask.

  • It is not known if face shields provide any benefit as source control to protect others from the spray of respiratory particles. CDC does not recommend use of face shields for normal everyday activities or as a substitute for cloth face coverings.
  • Some people may choose to use a face shield when sustained close contact with other people is expected. If face shields are used without a mask, they should wrap around the sides of the wearer’s face and extend to below the chin.
  • Disposable face shields should only be worn for a single use. Reusable face shields should be cleaned and disinfected after each use. Plastic face shields for newborns and infants are NOT recommended.


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