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Mask Fit Matters – Don’t Share Your Air

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  • Masks
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    Guidance for best mask wearing practices


    Mask Fit Matters

    Do’s and Don’ts

    How to Up Your Mask Game

    Which Types of Masks are Best, and Where to Find Them

    How to Care for Your Masks


    Mask Guidance

    Mask Fit Matters

    Why Wear a Mask?

    Covid-19 is airborne, highly contagious, and can cause serious long-term health effects for anyone who is infected. Transmitted through aerosols, the virus can linger in the air and spread further than six feet, like smoke. Even vaccinated people can be contagious and breathe out the virus before they have symptoms. Breathing in the virus is how it infects you. Masks and respirators help to prevent you from becoming infected.

    Learn more:

    Covid-19 is airborne and highly contagious. You become infected mainly by inhaling aerosols which are exhaled by an infected person (“source”), even if they are vaccinated and feel well.

    The virus in these aerosols is more concentrated in the air around the source, but they float and spread like smoke and linger in the air for hours, even if the source has left the room. While social distancing helps, when you’re indoors or in outdoor crowds, ultimately everyone is breathing in some of each other’s air.

    The probability of encountering a contagious person is high, and it’s not always apparent.

    Covid is contagious for a few days before symptoms start, and about half of all infections are spread by people before they realize they are sick. While Covid tests are helpful, accuracy varies and there are many false negative results. Vaccines reduce the chance that an infection results in a severe case or death, but breakthrough infections are common and they can become severe. Long Covid can happen to vaccinated or unvaccinated individuals who have even mild cases, with potential for damage to the lungs, brain, heart, kidneys and other organs. 

    So, while it takes a combination of several layers of protection to stop transmission, the most effective measures are those that prevent us from sharing our air.

    How Do Masks Work?

    Masks and respirators reduce the risk of COVID infection by reducing the amount of virus in the air we share. They accomplish this by filtering exhaled and inhaled air through the mask’s filtering material. Higher quality masks filter more effectively than cloth or surgical masks.

    Learn More

    Why Does Mask Fit Matter?

    COVID is so contagious that even short exposures with poor protection can result in infection.  A well-fitted, high-quality mask or respirator such as an N95, KN95, KF94, FFP 2 or elastomerics will form a complete seal around the face of the wearer, so that both inhaled and exhaled air is filtered through it. However, gaps between the mask and the wearer’s face allow unfiltered air to flow around the mask. Lower-quality masks, such as surgical masks which aren’t modified for best fit, or cloth masks, offer much less protection.

    Learn more:

    Masks/respirators and ventilation are our first lines of defense against getting infected with Covid-19. But all masks are not created equal – fit and filtration make a big difference in how well your mask will protect you and others.

    The level of protection given by a mask depends on its design. Protection can be thought of as the ratio of contaminant concentration outside to inside the mask (equipment can measure this ratio, and, less effectively, the senses). The protection also depends on proper fit (minimizing leakage), proper usage, and filter efficiency.

    When everyone present is wearing well-fitted, high-filtration N95, KN95, KF94, FFP2 or elastomeric masks/respirators over the nose and mouth, especially when combined with good ventilation and vaccination, the chance of infection is greatly reduced.

    A well-fitted mask/respirator is one that forms a full and complete seal around the face of the wearer. Ideally, all of the exhaled air passes through the particle (aerosol) filtering material that the mask is made of, and none of the air passes through gaps, holes, or loose connections between the wearer’s skin and the seal of the mask.

    But when wearing masks that don’t filter well, like cloth masks, or don’t fit well, like unmodified surgical masks, the chance of getting infected or spreading infection to others is higher than with a high-quality mask. Without any mask, it can take only seconds to minutes to get infected, even when socially distanced, and wearing a mask below the nose is like wearing no mask at all.

    How Can I Up My Mask Game?

    Choose the highest quality mask or respirator available that fits you well. Adjust and check your fit with each use, and wear it consistently when indoors with others or in crowded outdoor environments. Add eye protection for enhanced safety.

    Learn more
    Find Resources and Products

    What Are The Main Do’s and Dont’s?


    • Do choose a well-fitted, high-filtration (N95, KN95, KF94, FFP2 or elastomeric) mask. If these are not available to you, choose a multi-layer mask with a high quality filter that fits you well. Consider a mask brace or fitter.
    • Do handle your mask by the straps with clean hands. Avoid touching the inside of your mask so that you don’t contaminate it, and avoid touching the outside of your mask so you don’t contaminate your hands.
    • Do consider shaving or closely trimming a beard. Some beard styles may cause a gap between your mask and your face which can allow unfiltered air to get inside the mask. If you need to keep your beard, use a mask fitter or brace to press the mask firmly against your face.
    • Do keep your mask on, covering your nose and mouth at all times when indoors or in outdoor crowds with others.
    • Do go outside or enhance ventilation/filtration of the air and socially distance when taking off your mask to eat and drink to reduce risk, though eating indoors with others in this manner is still risky.
    • Do minimize the amount of time you are unmasked if you must unmask indoors. If you must eat indoors, choose better ventilated and socially distanced locations, lift your mask when taking a bite or sipping fluids (drink through a straw if possible), avoid touching the inside of the mask, and restore your mask while chewing. This technique can be tricky to execute perfectly, and it is not foolproof – for example, other people can come close before you realize it – so again, eating indoors with others is always risky.


    • Don’t wear a mask that fits loosely and leaves gaps, or is too uncomfortable to keep on.
    • Don’t wear a mask that is damp, soiled, damaged, or has become harder to breathe through.
    • Don’t remove your mask:
      • While speaking, even if distanced – that’s when you emit even more aerosols!
      •  When seated – you are still sharing indoor air, regardless of distance.
    • Don’t crowd, lean in close to people to speak, or sit very close to others.
    • Don’t turn up the music above conversation level.
    • If you choose to dine indoors (very risky!):
      • Don’t sit in a crowded, poorly ventilated area.
      • Don’t linger – keep duration short.
      • Don’t leave your mask off throughout a meal – keep it on when not actively eating or drinking, and if possible, put back on while chewing.

    How to Up Your Mask Game

    Choose a mask with the best possible fit and the best possible filtering efficiency. While almost any mask is better than no mask, aim for the best available protection.

    Check and Maximize the Fit.

    Your mask should create a tight seal all around with no air leaking around the edges.

    Do a fit test: 

    1. Put on the mask, making sure the nose wire is rounded tightly against the bridge of your nose. For KN95s, which come folded with a sharp central crease, flatten the wire before fitting to avoid a sharp peak over your nosebridge that allows air to enter and escape. 
    2. If the mask has two straps that go around your head, make sure one strap is above your ears and one below.
    3. Lightly hold the mask in place and inhale sharply. While inhaling, see if you feel a sensation of air or coolness around the edges of the mask, especially the area around your nose.
    4. Next, without holding the mask, exhale normally and pay attention to whether the flow of air goes around the edges of the mask or through the mask. 
    5. If you feel air leaking around the edges, adjust the mask and try again:
      • Try rounding the nose wire around the pad of your thumb or finger after flattening the wire.
      • Devices like strap adjusters, earloop toggles, or an external mask brace can help seal the leaks. Avoid under-mask brackets as they can worsen the fit.
      • The knot-and-tuck technique may improve the fit of medical masks, but avoid crossing the ear loops as this can worsen side gaps.
      • If your eyeglasses are fogging or your eyes feel drier than normal when you wear the mask, you may still be having some upwards leakage of air when you breathe out. Facemask tape products can help.
      • After adjusting, if the mask is still leaking, try a different model.

    For best filtering, choose the highest possible quality of material that has been designed for respiratory protection.

    Ensure authenticity: Avoid fakes – see Resources below.

    Add eye protection: Infection by particles entering the eyes is also possible anytime you are in a space where the air may be dense with airborne particles, such as a high-occupancy, poorly ventilated environment or one where the ventilation adequacy is unknown. Combine a mask or respirator with non-fogging goggles or other eye protection for improved safety. Even using prescription or non-prescription glasses provides some defense against infection.

    Which Types of Masks are Best, and Where to Find Them:

    As each new variant demonstrates an increasingly higher transmission rate, it takes a smaller and smaller exposure to cause infection. To reach the same level of protection that we had against earlier variants, we have to improve the quality of our masks. We currently recommend using at least an N95 respirator mask—which have headloops rather than earloops—an elastomeric mask, or a PAPR.


    PAPR – Powered Air Purifying respirators.

    • A PAPR consists of an enclosed headgear (half mask, mask or hood) with a fan, filter and power source. 
    • It pumps in filtered air for you to breathe.
    • Some models also filter your exhaled air, but traditional PAPRs (e.g. 3M) may not have filtered exhalation valves. These models as-is will only protect you, not others, but they can often be combined with another mask.

    Top Quality

    Elastomeric half facepiece or full facepiece reusable respirators.

    • Full facepiece respirators also provide eye protection.
    • Very protective for health care workers with heavy exposure to Covid-19, but anyone can wear these.

    High Quality


    • N95, KN95, KF94, FFP2 masks are classified as respirators.
    • Worn correctly, they provide about 95% filtration of airborne particles.
    • Choose models with headloops over ear loops to provide better fit. NIOSH approved N95 models have headloops.


    Surgical masks of high quality (ASTM 3) WITH modifications.

    • According to CDC, surgical masks are only intended for droplet/splash protection. They are NOT classified as respiratory protection against aerosols and therefore are not generally adequate against Covid, though modifications can improve their protectiveness.
    • The material filters very well, but they fit so loosely that they may block less than 50% of aerosols.
    • Knot-and-tuck technique or use of earloop toggles brings filtration efficiency up to ~75% (see video in Resources).
    • Sealing the leaks by adding a mask brace brings filtration efficiency up to ~90%.
    • Avoid crossing the earloops or wearing a mask bracket underneath the mask  as this may worsen fit.

    Layering cloth AND surgical masks in the right combination.

    • Well-fitted, 3-ply 100% cotton mask with adjustable nose wire worn over a 3-ply/ASTM3 surgical mask.
    • The cotton mask acts as a brace over the surgical mask.
    • Pros: Good in a pinch. Up to  ~85 – 95% filtration efficiency.
    • Cons: Harder to breathe; filtration varies with different products.

    Fair (not adequate for highly transmissible variants now circulating)

    • Well-fitted 3-layer cotton mask with a nose wire.
    • Well-fitted 2-layer cotton mask with a filter pocket and a nose wire.
    • Unmodified surgical mask.

    Poor (least protection, mostly decorative)

    • Single layer cloth masks or gaiters, made of materials that don’t block the light.
    • 2-3 ply cloth masks with no modifications: ~20–21% filtration efficiency.
    • Valved masks (don’t protect others).
    • Any product that fits loosely, leaving gaps.

    Notes: Anything that sits below the nose or mouth does not provide protection. Face shields can provide partial eye protection and can help extend the life of a mask or respirator, but they do not block aerosols.

    How to Care for Your Masks

    • High quality N95/KN95/KF94 respirators can be reused if they are taken care of according to the following guidelines. 
    • Reuse respirators or surgical masks only if they are clean and dry, with minimal wear and tear.
    • Store used respirators or surgical masks in a clean, breathable paper bag at normal room temperature and reuse after five or more days. 
    • To maintain hygiene, handle your mask only by the straps, with clean hands when putting it on, and clean your hands after storing or disposing of a used mask.
    • For daily use, cycle between 5 – 7 (or more) masks. Label bags for each mask by the day of use and replace each mask in the labeled bag after each use, making a non-penetrating checkmark on the outside of the bag each time, to keep track of the number of times used.
    • Most high quality N95/KN95/KF94 respirators can be reused about five times, other than those with changeable filters which are designed for re-use, e.g. elastomerics such as EnvoMask, FloMask or Breathe99. Follow manufacturer recommendations for maximum length of use for each type of filter, which can vary from 20 – 40 hours.  
    • Inspect masks or respirators before reuse. Discard it they are damaged, soiled, or look worn-out, or if it is becoming more difficult to breathe through or to adjust due to changes in shape, loosened straps, or any other reasons.
    • Carefully fold disposables in half without shaking them out, with the inside surfaces touching each other, then cut the strings with scissors to prevent risks to wildlife.
    • Dispose of them carefully in a covered trash can, or place in a plastic bag first if only open receptacles are available, and keep out of reach of children or animals. At this time, surgical masks cannot be recycled. 
    • Do not expose used masks or respirators to excessive heat (hair dryers, microwaves, ovens)
    • Do not clean masks or respirators with disinfectants, sanitizing wipes, bleach, alcohol, etc, and do not wash respirators and surgical masks.
    • Wash and fully dry cloth masks after every use, by machine if possible, in the warmest water and highest dryer setting for the fabric type, using any kind of laundry detergent or soap. Cloth masks can be machine washed with the rest of your laundry. 
    • Follow manufacturers’ care instructions for elastomerics or other reusables.


    World Health Network Graphics: Covid is Airborne – The science behind safer indoor gatherings

    World Health Network Resources: Ventilation, Filtration and Masks

    Graphics – Explainer Comics: The Quest of the Virosols

    About Masks

    Relative protectiveness of different masks in different circumstances

    Risk of Covid-19 infection with and without masks

    American Mask Manufacturers Association graphics: Choosing the Right Mask

    CDC: Understanding the difference between surgical masks and respirators

    What is a PAPR?

    Eyes can be infected by Covid-19: 4 things to know

    National Library of Medicine Graphics: How to (and how not to) wear a face mask

    Wearing a mask under the nose is equivalent to not wearing one at all

    Face mask fit modifications: mask braces and layering

    How to Knot and Tuck Your Surgical Mask to Improve Fit

    Mask Nerd Video: Layering and Mask Fitters (braces)

    DIY How to do a Mask Fit Test at Home: Poor Man’s Fit Test

    DIY (figure 2)

    Facial Hairstyles and Respirator Fit

    Where to Buy Authentic Masks and Accessories 

    3M Versaflo PAPRs are on Amazon (example 1 and example 2) and other resellers.


    Microclimate PAPRs Non-profit clearinghouse for verified products, proceeds are used to provide equitable access

    3M Aura

    Powecon KN95

    KN95 and KF94

    EnvoMask Reusable N95 with soft gel seal and changeable filter

    Armbrust Elastomeric Breathe99

    FloMask Elastomeric – two adult and one child size available

    Fix The Mask – Mask brace to improve surgical mask fit

    Foam Nose Bridge Pad (helps fill gaps)

    MaskTite Face Mask Tape

    Facemask Tape – Cabeau

    Facemask Tape – Pro Face Mask Tape

    How to Spot Fakes  

    CDC: How to identify a NIOSH-approved N95

    Mask Nerd: Mask Product Comparison Data – Look at Filtration Efficiency Column

    How to Implement a Safe Reuse Strategy to Reduce the Risk of Self-Contamination 

    CDC: Implementing Filtering Facepiece Respirator (FFR) Reuse, Including Reuse after Decontamination, When There Are Known Shortages of N95 Respirators

    Note: Covid Action Group/World Health Network has no commercial interest in any referenced products or resources.

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