N95 Mask vs Cloth vs Disposable vs Surgical Masks vs KN95 masks: Best Face Masks for Coronavirus
As of February 1, 2021 masks must be worn by passengers on all forms of public transportation (e.g., airplanes, ships, ferries, trains, subways, buses, taxis, ride-shares) traveling into, within, or out of the U.S. (CDC January 29, 2021).
- Cloth masks should be made with two or more layers of a breathable fabric that is tightly woven (i.e., fabrics that do not let light pass through when held up to a light source). If gaiters are worn, they should have two layers of fabric or be folded to make two layers.
- Masks should fit snugly but comfortably against the side of the face.
- Masks should be a solid piece of material without slits, exhalation valves, or punctures.
Face shields and goggles can be worn with masks, but cannot be worn instead of a mask.
Governments in several European countries have gone a step further, and, in January, mandated the use of masks or respirators documented to provide at least 80 to 95% filtration efficiency in public areas, particularly on public transport and in shops. Respirators in Europe are referred to as filtering facepieces, or FFPs, and are classified as FFP2 (filtering ≥94% of aerosols, total inward leakage <8%) or FFP1 (filtering ≥80% of aerosols, total inward leakage <22%). Austria has the most stringent requirement, requiring FFP2 masks, which provide similar levels of filtration as N95 and KN95 masks.
Which is the Best Mask to Prevent COVID-19?
Masks can be used alone or, for increased protection, particularly for the eyes, with a face shield — which we have also reviewed.
Here's what we cover in this answer:
- Why You Should Wear a Mask -- and Why It Should Be an Efficient One
- Best Combination of Materials For a Mask
- How Cotton and Other Household Fabrics Compare in Blocking Coronavirus
- Best Materials for Mask Filters
- Best Cloth Masks
- Best KN95 (Respirator) Masks
- Best Disposable Surgical/Medical Masks
- Other Types of Masks and Respirators
- Cleaning and Caring for Masks
- How to Improve Mask Fit to Reduce Leakage
- How to Reduce Eyeglass Fogging
- Concerns About Co2 Build Up
- Concern with Inhaling Microplastics
- Are Copper Masks Better?
- What Masks Protect Against Wildfire Smoke?
Along with social distancing, a mask provides additional protection from infecting others as well as preventing exposure. In addition, according to the CDC, "cloth mask materials can also reduce wearers' exposure to infectious droplets through filtration, including filtration of fine droplets and particles less than 10 microns." A review of studies found that transmission of SARS-CoV-2 and related coronaviruses was 82% lower with physical distancing of 1 meter (3.3 feet) or more, compared with shorter distances, and protection might increase with additional distance. Face mask use could result in an 85% reduction in risk of infection versus no face mask, with stronger associations for N-95 or similar respirators, while surgical masks and multi-layered cotton masks were less effective but offered more protection than single-layer masks (Chu, Lancet 2020).
An analysis of rates of growth of COVID-19 infection in U.S. states found that the mandated use of masks in public issued by 15 states in April and May, 2020 was associated with a decline of about 1% in the daily COVID-19 growth rate within the first week of the mandates and a 2% decline 21+ days after mandates were issued. Although the effect is modest, the researchers estimated that by May 22, 2020, 230,000 to 450,000 COVID-19 cases may have been averted due to the mandates (Lyu, Health Aff 2020).
As wearing a mask may reduce the amount of virus to which a wearer is exposed, it has been postulated that even if a mask-wearing person becomes infected, the reduced viral load to which they were exposed may mean that they suffer a milder disease. Supporting this theory is a study that showed that hamsters protected with a surgical mask partition were less likely to become infected with SARS-CoV-2 than those without the partition, and those that did get sick had milder illness. In addition, on cruise ships with COVID-19 outbreaks, the majority of infected patients (81%) were asymptomatic on a ship that had provided masks to all passengers and staff compared to only 18% of cases being asymptomatic on a cruise ship without masking (Gandhi, J Gen Intern Med 2020; Gandhi, N Engl J Med 2020).
Although CDC guidelines do not currently include the use of face masks at home, the rate of transmission from one household family member to another was 79% lower when members wore face masks prior to the first member developing COVID-19 symptoms, according to a study of 124 families in Beijing in which there was at least one infected person. Overall, there was a 23% rate of transmission of COVID-19 from an infected family member to another, but this was no lower when mask wearing began after the first member developed symptoms. These results are consistent with the fact that viral load is highest two days before symptoms and on the first day of symptoms. Daily use of disinfectants reduced transmission by 77%. Transmission rates were four times higher if the primary case had diarrhea and 18 times higher when there was frequent daily close contact (less than 3 feet apart). The researchers recommended use of face masks in families in which a member has been at risk of getting infected. In China, over 70% of transmission occurred within families (Wang, BMJ Global Health 2020).
Currently, both the CDC and WHO provide basic guidelines for choosing a cloth mask.
According to CDC guidelines, a cloth mask should:
- Use a minimum of 2 - 3 layers, preferably with batting between the layers
- Use fabrics with high thread count and fine weave, water-resistant fabric, and hybrid fabrics such as cotton-silk, cotton-chiffon, or cotton-flannel (cotton blends may be better than pure cotton). (In addition, the CDC notes that, due to their electrostatic charge, materials such as polypropylene may enhance filtration efficacy and fabrics such as silk can help to repel droplets.)
- Cover the nose and chin
- Fit snugly on the sides of the face without gaps
- Be secured with ties or ear loops
- Use ties rather than ear loops because ties provide better fit
In addition, the CDC warns not to choose masks that are:
- Made of fabric that makes it hard to breathe, such as vinyl
- Have exhalation valves or vents, as this allows virus particles to escape
- Intended for healthcare workers, such as N95s and surgical masks
1. Innermost layer: Hydrophilic material (i.e., one that can absorb moisture, such as cotton or cotton blends)
2. Middle layer: Hydrophobic material (i.e., repels moisture) of synthetic non-woven material such as polypropylene or a second cotton layer which may enhance filtration or retain droplets.
3. Outermost layer: Hydrophobic material (e.g., polypropylene, polyester, or their blends) which may limit external contamination from penetration through to the wearer's nose and mouth.
Note that polypropylene, a material often used to make disposable surgical masks, has an electrostatic charge which can improve the filtration efficiency of masks. Polypropylene "spunbound" is sold in fabric and many other retail and online stores under brand names such as Oly*fun and Pellon. Polypropylene is sold in different weights (measured in grams per square meter or GSM). Most commercially manufactured surgical masks are made of 3-ply 25GSM. Polypropylene materials between 25 and 40 GSM tend to have similar filtration efficacy and breathability, while polypropylene 60 GSM has a higher filtration efficiency but less breathability (Zhao, Nano Lett 2020). Be aware that some forms of polypropylene should not be machine washed.
See below for a more detailed discussion of the filtration efficacy of various cotton and synthetic household fabrics.
ASTM International, an independent, non-profit organization that sets testing and performance standards for medical masks and other personal protective equipment (PPE) is currently developing specifications for cloth face coverings. The specifications are expected to be published in early 2021.
The first study, from the University of Illinois at Urbana-Champaign, found that many household fabrics can be as effective as the material in surgical masks for blocking droplets of sizes known to carry the COVID-19 (SARS-CoV-2) coronavirus. The blocking efficiency of a commercial medical mask was found to be 96.3%, while the blocking efficiency of a used (85% polyester and 15% nylon) was slightly better -- 97.9%. In addition, most household fabrics were more breathable than the material in a medical mask. The dish cloth, for example, was twice as breathable as the medical mask (Aydin, medRxiv 2020 --preprint). (See the CDC website to learn how to make a cloth face covering.)
A study at the University of Chicago and Argonne National Laboratory found that (600 thread-per-inch (TPI) sheet by Wamsutta) was more effective in filtering large droplets (similar to larger-sized SARS-CoV-2 droplets) than loosely woven cotton with a lower thread count (, 80 TPI), while fabrics with an electrostatic charge (such as ) were best for blocking aerosols -- the smaller sized droplets that remain suspended in air for extended amounts of time. Using layers of both fabrics, together, was most effective for blocking both large and small droplets. For example, two layers of 600 TPI cotton fabric had a large particle and small particle blocking efficacy of 99.5% and 82%, respectively, but one layer of 600 TPI cotton combined with two layers of chiffon (90% polyester, 10% spandex from Jo-Ann Stores) had a large particle and small particle blocking efficacy of 99.2% and 97% -- which, at low airflow rates (i.e., when not all air is drawn through the mask) is nearly as good as a properly-fitted N95 mask for blocking large particles and better than the N-95 with respect to small particles, of which only 85% are blocked by an N-95 mask). The researchers also found that small holes or leaks around the edges of the fabrics could decrease the blocking efficacy by 50% or more, and emphasized the importance of a good fit (snug and without gaps) (Konda, ACS Nano 2020). [Note: An illustration in the study shows the electrostatic layer of fabric as the inner layer when fabrics were combined. However, ConsumerLab contacted the author of the study who suggested that electrostatic fabric (such as chiffon) may be best used as the outer layer of the mask to avoid humidity from the nose or mouth, which could interfere with the electrostatic properties, but emphasized that was his suggestion, not something that was tested in the study.]
In another study, researchers at Florida Atlantic University tested masks made from common household fabrics, as well a typical "cone" mask (often sold at pharmacies) to see how well they worked to stop droplets using a simulated model of coughing (a mannequin head through which liquid was manually pumped). Without any covering, droplets from the simulated cough traveled an average of 8 feet. With a (single-layer, elastic T-shirt material, 85 threads per inch) droplets traveled an average of 3 ft. 7 inches, with a (as shown in this instructional video
Rather than focus on how far droplets travel, researchers at Duke looked at how well different masks block droplets during speaking. A fitted N95 mask without a valve was most effective in retaining droplets, with less than 1% of droplets being transmitted. The next most effective, in order, were a 3-layer , a cotton--cotton "apron" mask, a 2-layer polypropylene mask, a 2-layer cotton pleated mask, and then an N95 with a valve.
The Duke researchers found that two masks offered little protection: A was only slightly more effective than using no face covering at all, while the worst face covering was a (often worn during running or sports) that showed a 10% increase in the number of droplets. The researchers suggested that the neck fleece material breaks larger liquid droplets into smaller droplets than can more easily be dispersed into the air (Fischer, Sci Adv 2020 — includes photos of the masks but no details about origin or brands). .
When doubled over, some neck gaiters may be more effective than a triple layer, all-cotton cloth mask. A study conducted by researchers at the CDC and National Institute for Occupational Safety and Health (NIOSH), found that a single-layer polyester neck gaiter (FKGIONG Sun UV Protection Neck Gaiter, 95% polyester, 5% Spandex) blocked 47% of outward moving cough aerosols (ranging in size from 0 to 7 microns) and when doubled over, blocked 60%. This was slightly better than a medical procedure mask with ear loops, which blocked 59% and a cloth mask made of 3 layers of cotton fabric and ear loops (Hanes Defender), which blocked 51%. An N95 respirator blocked 99% (Lindsley, medRxiv 2020 -- preprint). It should be noted that the cotton cloth mask tested did not have an outer layer made of hydrophobic material (such as polypropylene or polyester) as recommended by WHO. If wearing a neck gaiter, make sure it fits securely and consider choosing one with an adjustable cord, to help prevent it from falling down (off of the nose and mouth) during strong sudden movements, such as during a sneeze.
A study that evaluated how well masks protect the wearer from breathing in small particles (ranging in size from 0.02 to 0.6 microns) and factored in the fit of the mask as well as its filtration efficiency found that a NIOSH approved N95 (3M 9210) had the highest filtration efficiency at 98%, followed by 80% for a medical procedure mask with ear loops (Cardinal Health) with nylon hosiery placed over it, and 71.5% for a surgical mask with ties. [Note: The filtration efficiency of the medical procedure masks can range dramatically depending on how it was worn.] The filtration efficiency was 74% for a 2-layer woven nylon mask with ear loops (Easy Masks LLC) with an aluminum nose bridge and nonwoven filter insert which, interestingly, had a slightly higher filtration efficiency after being washed once, 49.9% for a folded, cotton bandana, 39.3% for a single-layer woven polyester/nylon mask with ties (Renfro Corporation), 37.8% for a single-layer woven gaiter/neck cover balaclava bandana MPUSA LLC), 28.6% for a nonwoven polypropylene mask with fixed ear loops (Red Devil Inc), and just 26.5% for a 3-layer woven cotton mask (100% cotton) with ear loops (Hanesbrands Inc) (Clapp, JAMA Intern Med 2020).
As discussed above, the WHO recommends that the middle layer of a cloth mask be made of a synthetic, nonwoven fabric such as polypropylene, or a second layer of cotton (high thread count cotton has been shown to have better filtration efficacy than lower-thread cotton). Many cloth masks that you can buy online come with a "filter pocket" as the middle layer, which you can buy pre-made filters for, or add your own. We've reviewed common materials for making mask filters, including Filti Face Mask Material and Medline Dry Baby Wipes, as well as materials such as polypropylene and other non woven fabrics (100% polypropylene, Pellon Sew-In Interfacing and Oly*fun), cotton and quilter's cotton.
If you prefer to purchase a cloth mask, we reviewed many masks sold online and . We also considered features that can affect fit and comfort, such as adjustable/bendable nose wires and adjustable straps, which can be particularly important for people who wear glasses or hearing aids. We also reviewed oversized masks designed to accommodate beards or to be used when singing, and masks with clear panels to enable lip reading by others.