By Iva Kljajevic / Date
Source: PAHO
Since March 2020, almost the entire world has been affected by the coronavirus pandemic. This was followed by numerous lockdowns, police hours, mandatory hand disinfection and wearing masks indoors, and making a distance of at least 2 meters in rows.
Many people found themselves in unknown situations, they didn’t know what kind of virus it was and how they can best protect themselves. Today, almost two years after the start of the pandemic, although the vaccine is already widely available to citizens, it’s still mandatory to wear masks indoors.
But instead of wondering which mask to wear on which occasion, let’s just make sure it never happens again.
The following are five questions about masks that always stump people—and the answers you should know.
How many different types of masks are there?
There are a total of 7 types of masks that protect against the transmission of the COVID19 virus:
- A cloth face mask – fits against the face using either ear loops or ties around the head, multiple layers of breathable fabric create a barrier between the nose and mouth and the outside and help contain any respiratory droplets people may breathe out
Source: Food52 - A surgical mask – a disposable cover usually worn by medical professionals as personal protective equipment (PPE) during surgeries or other procedures, and it’s often made of a combination of paper and plastics. Surgical masks come in two main types:
- flat-pleated or duck-billed in shape, conforming to the bridge of the nose with a flexible piece, affixed to the head with two ties
- pre-molded, conforming to the bridge of the nose with a flexible piece and adhering to the head with a single elastic
Source: Healthline
Source: USA medical and surgical supplies
- Masks with exhalation valves or vents – easier to breathe through and more comfortable, are appropriate when the mask is meant to protect the wearer, for instance, can protect workers from dust at a construction site or hospital workers from infected patients
Source: Carl Roth - An N95 respirator and other professional – grade medical masks – carefully sized to form a tight seal between the air outside and the face they are designed to protect healthcare workers from droplets in the air
Source: IndiaMART - A medical mask/N95 filtering facepiece respirator – combines the properties of surgical masks and respirators, can protect against inhaled particles, resists fluids, limits the dispersion of exhaled properties, and is regulated by both NIOSH and FDA
Source: Amazon - Clear masks or cloth masks with a clear plastic panel – the alternative type of mask for people who interact with people who are deaf or hard of hearing, young children or students learning to read, students learning a new language, people with disabilities, and people who need to see the proper shape of the mouth for making appropriate vowel sounds
Source: Prevention.com - Face shields – clear sheets of plastic that hang down from a headband, covering the face from the top of the head to below the chin.
Source: Cleaning Supplies 4U
How effective is each at protecting against COVID-19?
Gauze or woven cotton masks can reduce concentrations of aerosol particles and certain water-soluble gases and vapors at pressure drop acceptable for respiratory protection during accident conditions (Cooper et al., 1983a) and when such materials are used in combination with improvised techniques to improve the face fit (e.g., nylon hosiery), leakage can be reduced (Cooper et al., 1983b). More effective fabrics for cloth masks are tightly woven fabrics, such as cotton and cotton blends, and breathable materials with two or three fabric layers. Less effective fabrics for cloth masks are loosely woven fabrics, such as loose-knit fabrics, and single-layer materials. A US EPA study shows three-layer knitted cotton mask block an average of 26.5 percent of particles in the chamber, and a washed, two-layer woven nylon mask with a filter insert and metal nose bridge blocks 79 percent of particles on average.
Source: Honeywell Store
Source: Global Sources
Surgical masks are highly effective if you’re a carrier of the virus because they help you not to transmit it to people around you. The collection efficiency of surgical mask filters is extremely variable and studies were showing differing penetration ranges depending on the size of the particles and the test methods used (Cooper et al., 1983b; Tuomi, 1985; Brosseau et al., 1997; McCullough et al., 1997; Willeke and Qian, 1998). A US EPA study shows surgical masks with ties provide 71.5 percent filtration, and surgical masks with ear loops only provide 38.1 percent filtration.
CDC doesn’t recommend using masks with exhalation valves or vents because the hole in the material may allow your respiratory droplets to escape and reach others, but the research on the effectiveness of these types of masks is ongoing.
Respirators are very effective when persons pass a detailed test of the mask’s fit, but, unfortunately, it’s a service that’s currently only available to healthcare workers. Health-care workers who wear most N95 filtering facepieces without prior fit-testing fail to achieve the expected levels of protection and persons passing a qualitative or quantitative fit test will achieve the expected level of protection, according to Coffey et al., (2004). A US EPA study shows both expired N95 masks and sterilized N95 masks provide the same level of protection as new N95 masks with greater than 95 percent filtration.
You should wear face shields to provide an extra layer of protection when you’re in sustained proximity with others, but they don’t provide a barrier to respiratory droplets, which can come up under them. They’re primarily used to protect the eyes of the person wearing them, their effectiveness is still unknown and an evaluation is ongoing.
What is the best one to protect against COVID-19?
Masks that should be prioritized for healthcare personnel are N95 respirators approved by CDC’s National Institute for Occupational Safety and Health (NIOSH) because they filter out both large and small particles when the wearer inhales. An N95 filtering facepiece is likely to be both the least expensive and the most widely available NIOSH-certified respirator when selecting a personal protective device for healthcare workers and the public for protection against airborne infection. A respirator is designed to protect the wearer from hazardous contaminants in the air and most N95 filtering facepiece respirators aren’t designed to protect the wearer from splashes of body fluids. There’re some N95 filtering facepiece respirators called surgical N95 respirators that have this additional feature and they’re certified by NIOSH as well as regulated by FDA. The N95 filtering facepiece respirators are considered disposal devices and aren’t designed for either extended use or reuse after cleaning and disinfection. However, researchers are testing ways to disinfect and reuse them.
After the emergence of the omicron variant, which is twice as contagious as the delta variant, experts have found that surgical masks protect you better against the transmission of COVID-19 than any cloth mask, according to CNBC. A medical mask is intended to protect others from large droplets exhaled or released by the wearer and to protect the wearer’s respiratory tract from splashes of body fluids that may unexpectedly occur in the clinical setting, while a cloth mask is intended to trap respiratory droplets that are released when the wearer talks, coughs or sneezes and also acts as a barrier to protect the wearer from inhaling droplets released by others.
What are typical mask features?
The filtering materials for respirators and medical masks are usually non-woven and composed of synthetic thermoplastics, especially spun polypropylene. Fabric masks should be made of three layers of fabric that include an inner layer of absorbent material, such as cotton; a middle layer of non-woven non-absorbent material, such as polypropylene; and an outer layer of non-absorbent material, such as polyester or polyester blend.
Filtering facepiece respirators are part of a family of negative-pressure respirators and it means that the pressure inside the facepiece becomes negative when the wearer inhales a breath of air. Any leakage along the sealing surface of the face will allow hazardous contaminants to bypass the filtering element and be inhaled during the negative-pressure period (about half the time a respirator is worn). Wearers of negative-pressure respirators must be clean-shaven because facial hair has been shown to interfere with the sealing edge of the respirator.
Source: ResearchGate
Some N95 filtering facepiece respirators have the exhalation valves placed near the mouth of the wearer that bypasses the filter media, significantly reduces the effort required to exhale, and also increases the wearer’s comfort as there’s less heat and moisture buildup. If a non-symptomatic, but infectious wearer is exhaling a virus or other pathogen, the virus or pathogen may bypass the filter, be emitted to the outside environment, and possibly infect individuals in the immediate vicinity (CDC, 2003).
Wear time affects the performance of the N95 and the longer the respirator is worn, the more particulate loading and moisture buildup from exhaled air occur, with possible obstruction of breathing. The filtering facepiece respirator may be deformed creating a suboptimal fit and increasing leakage when it’s often taken off and redonned.
A fluid-resistant disposable medical mask has a three-layered laminate structure of different nonwoven fabric materials that is pleated and sized to cover the wearer’s nose and mouth (Maturaporn, 1995):
- The innermost layer (the first ply) is made of nonwoven, airlaid4 paper material that’s resistant to liquid and designed to be soft, in contact with the wearer’s face, and intended to prevent facial hair, perspiration, and saliva from interfering with or exiting the facemask;
- The middle layer (the second ply) is made of nonwoven, liquid-resistant, melt-blown, polypropylene material designed to act as a barrier against bacteria, body fluids, and particulate contaminants;
- The outermost layer (the third ply) is made of nonwoven, liquid-resistant, thermo-bond, polypropylene fabric, designed to be the first contact filter barrier layer against body fluids and liquid particulate contaminants from outside the wearer’s medical mask.
Which ones help the most to protect you from COVID?
A WHO study recommends three types of masks for the public:
- Reusable non-medical masks which comply with the ASTM F3502 standard or CEN Working Agreement 17553, or a non-medical mask meeting WHO essential parameters;
- Disposable medical masks which comply with medical mask standards EN 14683 Type I, ASTM F2100 Level 1, YY/T 0969, YY 0469 (or equivalent);
- Other types of well-fitting non-medical masks, including homemade multi-layered masks that are acceptable options, when other options are not available.
Caregivers at any setting where they provided care to patients with suspected or confirmed COVID-19, including home care, long-term care facilities, and community care settings should wear a respirator or a medical mask. An N95 mask blocks particles less than 100 µm from being inhaled, reduces the transfer of respiratory droplets to others, blocks blood or other potentially infectious materials from reaching the wearer’s skin, or mouth and keeps droplets and larger particles from being inhaled, and requires filtration of all air reaching the mouth or nose for 5 µm particles and larger. A medical mask has all the same features as the N95 mask, except that it doesn’t block the passage of particles that are less than 100 µm, while woven cotton (or other fabric masks) and improvised protection have the feature to only reduce the transfer of respiratory droplets to others.
Which masks do you use most often and why did you decide on them in particular? Did the above information influence you to change your mind and decide to start using a different type of mask? Write to us in the comments.
References
Cooper, D.W., Hinds, W.C., Price, J.M. (1983a). Emergency respiratory protection with common materials. American Industrial Hygiene Association Journal, 44 (1): 1–6.
Cooper, D.W., Hinds, W.C., Price, J.M., Weker, R., Yee, H.S. (1983b). Common materials for emergency respiratory protection: Leakage tests with a manikin. American Industrial Hygiene Association Journal, 44 (10): 720–726.
Tuomi, T. (1985). Face seal leakage of half masks and surgical masks. American Industrial Hygiene Association Journal, 46 (6): 308–312.
Brosseau, L., McCullough, N., Vesley, D. (1997). Bacterial survival on respirator filters and surgical masks. Journal of the American Biological Safety Association, 2: 232–247.
McCullough, N.V., Brosseau, L.M., Vesley, D. (1997). Collection of three bacterial aerosols by a respirator and surgical mask filters under varying conditions of flow and relative humidity. Annals of Occupational Hygiene, 41 (6): 677–690.
Willeke, K., Qian, Y. (1998). Tuberculosis control through respirator wear: Performance of National Institute for Occupational Safety and Health–regulated respirators. American Journal of Infection Control, 26 (2): 139–142.
Coffey, C.C., Lawrence, R.B., Campbell, D.L., Zhuang, Z., Calvert, C.A., Jensen, P.A. (2004). Fitting characteristics of eighteen N95 filtering-facepiece respirators. Journal of Occupational and Environmental Hygiene, 1 (4): 262–271.
CDC. (2003). The cluster of severe acute respiratory syndrome cases among protected health-care workers—Toronto, Canada, April 2003. Morbidity and Mortality Weekly Report, 52 (19): 433–436.
Maturaporn, T. (Inventor). (1995). Disposable Face Mask with Multiple Liquid Resistant Layers. U.S. Patent.
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cloth-face-cover-guidance.html
https://www.nist.gov/news-events/news/2020/11/new-airflow-videos-show-why-masks-exhalation-valves-do-not-slow-spread
https://www.nap.edu/read/11637/chapter/4#35
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https://www.paho.org/en/news/28-2-2020-face-masks-during-outbreaks-who-when-where-and-how-use-them
https://food52.com/shop/products/9005-food52-adjustable-cloth-face-masks
https://www.healthline.com/health/coronavirus-mask
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https://www.indiamart.com/proddetail/n95-respirator-face-mask-22327371048.html
https://www.amazon.com/PHG-PROTECTIVE-HEALTH-GEAR-Professionals/dp/B08NXZ5JNC
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About the Author
Iva Kljajevic, MSc, is an experienced writer and research biologist with international experience.
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