Although the material of which surgical masks are made will filter out some viruses and bacteria by trapping the aerosol suspended in breathed air, they only provide partial protection from airborne diseases because of the typically loose fit between the mask edges and the wearer's face.[2][3][4] Surgical masks are distinct fromfiltering respirators, such as those made to the AmericanN95 standard, which are more airtight and purposefully designed to protect against finer airborne particles.
Comparison of breathing out without (top) and with (bottom) a mask. Note that without a mask jets of air are exhaled that can carry viruses and bacteria rapidly towards a person in front of the person breathing out. But with a mask these jets are blocked, meaning the air instead mostly rises due to convection. Note that although jets are blocked, the same amount of air moves in both cases, allowing the wearer to breathe easily.
Evidence fromrandomized controlled trials that surgical masks reduce infection from diseases such as influenza is weak.[5][6] Although a recent very large (over 300,000 people) study found some evidence that they reduced transmission in the community,[7] surgical masks can vary greatly in quality which may make these studies less useful.[3] The effect of surgical masks is partially attributed to filtering out some ofaerosol particles that are howairborne diseases are transmitted. Surgical masks are highly variable[3] but the material of which they are made typically filter out more aerosol particles than docloth masks but much less than does the material of whichN95,FFP2 and similar masks, are made.[8] This combined with the poor fit suggests that surgical masks offer some protection to airborne diseases such asCOVID-19 but less than doN95,FFP2 and similar masks.
There are standards for the materials masks are made from. For example, the European EN 14683 Type II standard requires the material of the mask to filter particles (mean diameter close to 3 micrometres) containing the bacteriumStaphylococcus aureus.[9][10] The bacterial filtration efficiency of the mask material is the fractional reduction in the number ofcolony-forming units (CFUs) when the aerosol is passed through the material. For a Type II mask under this standard, the material must filter enough of the aerosol particles containing the bacteria to achieve a CFU reduction of at least 98%.
ASTM International has an F2100 standard[11] with similar bacterial filtering standard to the European Type II standard but in addition uses a test aerosol of 0.1 micrometre particles. The Level 3 standard F2100 standard requires that these particles must be filtered out with at least 98% efficiency. Neither the European nor the ASTM standard tests performance as worn, they just test the material — the difference being the air leakage. This is different to personal protection equipment standards such asN95 andFFP, which do test performance as worn.
Surgical masks are made of anonwoven fabric created using amelt blowing process. They came into use in the 1960s and largely replacedcloth facemasks indeveloped countries.[12] The colored (usually dark blue, green, or occasionally yellow) side of the mask (fluid-repellant layer) is to be worn outwards, and the white side (absorbent layer) inwards.[13][14][15]
In someEast Asian countries, masks have often customarily been worn by people who are sick in order to avoid spreading it, to protect against air pollution or allergens, as a fashion statement, or to deter social interaction.[16][17][18] Theuse of surgical masks during theCOVID-19 pandemic was a subject of debate,[19] asmask shortage was a central issue.[20][21]
Shadowgraph videos of the outer airflow during a sneeze, comparing an unmasked sneeze with several different method of covering one's mouth and nose[23]
A surgical mask serves as a mechanical barrier that interferes with direct airflow in and out of respiratory orifices (i.e.nose andmouth). Most commonly used surgical masks are designed to only traprespiratory droplets, and therefore do not filter or block fine airborne particles that are smaller than the designed filtration ratings, which may be transmitted bycoughs,sneezes, unintentionalspitting during talking, or certain aerosol-generating medical procedures (e.g.bronchoscopy,laryngoscopy ordental procedures). Surgical masks also cannot provide complete protection fromgerms and other contaminants because of the often loose fit between the mask edges and the wearer's face,[24] especially when the mask is worn outright incorrectly (e.g. low with the nose and/or mouth exposed).
A surgical mask is adisposable device that creates a physical barrier between therespiratory tractopenings (nose andmouth) of the wearer and potentially pathogeniccontaminants in the immediate environment. If worn properly, surgical masks are meant to help block out most (if not all) large-particledroplets, splashes,sprays, or splatter that may containviruses andbacteria, keeping them from entering the wearer's nose and mouth.,[24] and conversely are also effective barriers for retaining large droplets released from the wearer's the mouth and nose.[22] Surgical masks help reduce exposure of the wearer'ssaliva and respiratory secretions to others[24] that could otherwise travel up to 7.9 metres (26 ft).[25] Surgical mask also remind wearers not to touch their mouth or nose, which could otherwise transfer viruses and bacteria after having touched acontaminated surface.[23]
A surgical mask is not to be confused with arespirator (which is specifically rated for sub-micron particles) and is notcertified as such. Surgical masks are not designed to protect the wearer from inhaling airborne bacteria or virus particles and are less effective than respirators, which are designed for this purpose.[22] Collection efficiency of surgical maskfilters can range from less than 10% to nearly 90% for different manufacturers' masks when measured using the test parameters forNIOSH certification. However, a study found that even for surgical masks with "good" filters, 80–100% of subjects failed anOSHA-acceptedqualitative fit test, and a quantitative test showed 12–25% leakage.[26]
Modern surgical masks are made from paper or othernon-woven material and should be discarded after each use.[27]
Asurgical team of (from left) operatingsurgeon,assistant andscrub nurse, all wearing masks with integral protective face shields and horizontally hand-tied straps.
The design of the surgical masks depends on the intended usages. Usually, the masks arerectangular shaped withpleats to allow the wearer to expand and curve the mask so it can better cover the entirety of the area from the nose to around thechin. The outward-facing side of the mask is typically colored (usuallyblue,green, oryellow) and made thicker, tougher, and water impermeable. The inner layers of the mask are made of three-ply (three layers)melt-blown polymer (most commonlypolypropylene) placed betweennon-woven fabric.[28] The melt-blown material acts as the filter that stopsmicrobes from penetrating and exiting the mask.[28] Some masks have an attached thinpolyethylenefaceshield (known as a "splash shield") to provide additionalspray protection over theeye area.[citation needed]
A different type of mask, known as "duckbill" masks, uses atrapezoidpouch-like design that has significantly shortened side edges — sometimes none at all — to minimize loose gaps that pathogens can leak past. These masks are typically made to the N95/P2 standards, and are commonly used for clinical situations that demand fineparticulates protection, such astuberculosis.
Small strips offoam or thickened fabric are often sewn along the top edge of the mask to help better seal away exhaledwater vapors (which can fog upeyewears and faceshields) and soak up excessperspiration dripping from above. Small bendable metal strips are frequently added to the top edge to better fit over thenasal bridge. Occasionallyadhesive tapes can also be added to secure the seal and prevent the mask from slipping up and down.
The masks are typically fastened to the head withstraps orelastic bands that are attached to the mask's four corners.[29] Straps come in four free-hanging ribbons that aremanually tied in two pairs horizontally around the back of the head, and are most frequently used insurgical operations due to the ability to customize the strap length and tension comfortably to the wearer's face shape and head movements. Elastic bands come in a pair of loops that can either be horizontally or vertically attached. Horizontal loops go around the head like tied straps, designed to exert tension on the top and bottom edges of the mask for firmer contact seal, and are usually seen on duckbill masks; while vertical loops hook around theears with less tension (due to the weakerrigidity of theelastocartilaginousauricles compared to thebonyskull) and thus less firmly secured to the face, but are more popular in non-procedural usages due to the ease of putting on and taking off.
Filter material in the middle layer may be made ofmicrofibers with an electrostatic charge; that is, the fibers areelectrets. An electret filter increases the chances that smaller particles will veer and hit a fiber, rather than going straight through (electrostatic capture).[30][31][32][33][better source needed][medical citation needed] While there is some development work on making electret filtering materials that can stand being washed and reused,[34] current commercially produced electret filters are ruined by many forms of disinfection, including washing with soap and water or alcohol, which destroys the electric charge.[35] During the COVID-19 pandemic, public health authorities issued guidelines onhow to save, disinfect and reuse electret-filter masks without damaging the filtration efficiency.[36][35] Standard disposible surgical masks are not designed to be washed.
Performance of surgical masks is evaluated based on such parameters asfiltration (mask capture of exhaled aerosols), exposure (transfer of aerosols from outside), mask airflow resistance (pressure difference during breathing, ΔP, also known asbreathability),[37] liquid penetration resistance, air and water vapor permeability, water repellency (for outer and inner surfaces).[38]
Face masks for use in surgery were developed in Europe by several physicians, includingJan Mikulicz-Radecki at theUniversity of Breslau andPaul Berger in Paris, in the late nineteenth century, as a result of increasing awareness of germ theory and the importance of antiseptic procedures in medicine.[40] In response to a pneumonic plague in Manchuria and Mongolia in 1910, Chinese-Malaysian epidemiologistDr. Wu Lien-teh greatly improved on the designs he had seen in Europe to develop a face mask of layers of gauze and cotton that would protect both the wearer and others.
Modern surgical masks began to be used in the 1960s. Their adoption causedcloth facemasks, which had been used since the late 19th century, to completely fall out of use in thedeveloped world.[41][42] However, cloth masks and surgical masks both continued to be used indeveloping countries.[43]
During theCOVID-19 pandemic, face masks or coverings, includingN95,FFP2, surgical, andcloth masks, have been employed as public and personal health control measures against the spread ofSARS-CoV-2, the virus that causesCOVID-19.
In community and healthcare settings, the use of face masks is intended assource control to limittransmission of the virus and for personal protection to prevent infection.[44] Properly worn masks both limit therespiratory droplets andaerosols spread by infected individuals and help protect healthy individuals from infection.[45][46]
Reviews of various kinds of scientific studies have concluded that masking is effective in protecting the individual against COVID-19.[45][47][48] Variouscase-control and population-based studies have also shown that increased levels of masking in a community reduces the spread of SARS-CoV-2,[47][48] though there is a paucity of evidence fromrandomized controlled trials (RCTs).[49][50] Masks vary in how well they work. FittedN95s outperform surgical masks,[51][52] while cloth masks provide marginal protection.[53][54]
During the public health emergency, governments widely recommended and mandated mask-wearing, and prominent national and intergovernmental health agencies and their leaders recommended the use of masks to reduce transmission, including theWHO,American,European, andChinese Centers for Disease Control and Prevention.
As the pandemic raged on, healthcare workers were required to continue wearing surgical masks for 12 or more hours a day. This caused the ear loops of the masks to chafe the back of their ears.Ear savers, plastic straps and hooks that go around wearer's heads, were invented to move the ear loops away from the wearer's ears. They could be made on demand by using3D printing process.[55]
A medical professional (anesthesiologist) wearing a surgical mask during an operation
A surgical mask is intended to be worn byhealth professionals during surgery and certain health care procedures[56] to catch microorganisms shed inliquid droplets and aerosols from the wearer's mouth and nose.[27] Evidence supports the effectiveness of surgical masks in reducing the risk ofinfection among other healthcare workers and in the community.[57] However, aCochrane review found that there is no clear evidence that disposable face masks worn by members of the surgical team would reduce therisk ofwound infections after cleansurgical procedures. However, the review cautioned that the studies examined are of low quality and that the result should not be generalized.[6]
Healthcare workers are trained in how to put on, handle, remove, and dispose of surgical masks. For healthcare workers, safety guidelines recommend the wearing of a face-fit testedN95 orFFP3respirator mask instead of a surgical mask in the vicinity ofpandemic-flu patients, to reduce the exposure of the wearer to potentially infectious aerosols and airborne liquid droplets.[58][59][60]
A face mask with Disney characters, designed for children[61]Passengers on public transport inMexico City wearing face masks during the2009 swine flu pandemic
In community and home settings, the use of facemasks and respirators generally are not recommended, with other measures preferred such as avoiding close contact, maintaining goodhand hygiene,[27] and wearing cloth face coverings.[62] Surgical masks provide some protection against the spread of diseases, and improvised masks provide about half as much protection.[63]
The custom of wearing surgical masks began in Japan in the early 20th century, when theSpanish flu pandemic swept the world and killed 20 to 40 million people. A second global influenza pandemic in 1934 established the use of surgical masks in Japan. Later, this custom spread to East Asia.[16]
In Japan and Taiwan, surgical masks have commonly been worn in winter months during theflu season by those who have respiratory illnesses as a courtesy intended to preventviral transmission.[16][64][65] People in Japan as well as Korea and China may also wear masks in any season because ofair pollution or allergies. Some younger Japanese people wear masks and audio headsets to signal a desire to avoid interaction.[16]Hay fever has been common in Japan since the 1980s, and as of 2019, 42.5% of the Japanese population suffers from some form of hay fever, with 38.8% suffering from cedar pollinosis, making the use of surgical masks more common in winter and spring.[66][67][16] On the other hand,acupuncturist Michelle M. Ching says that mask-wearing as a custom appeared in East Asia rather than other parts of the world also facing pollution and disease due to the historical influence ofTraditional Chinese Medicine and its ideas about air and wind.[16]
More recently, due to the rising issue ofsmog inSouth andSoutheast Asia, surgical masks andair filtering face masks are now frequently used in major cities in India, Nepal and Thailand whenair quality deteriorates to toxic levels.[68][69][70] Additionally, face masks are used in Indonesia, Malaysia and Singapore during theSoutheast Asian haze season.[71][72] Air filtering surgical-style masks are quite popular across Asia and as a result, many companies have released masks that not only prevent the breathing in of airborne dust particles but are also fashionable.[73][74] In Japan, some use masks as fashion statements, at times as a result of influence fromlolita fashion,black metal andK-pop stars.[17][18]
Surgical masks may also be worn to conceal identity. In the United States banks, convenience stores, etc. have banned their use as a result of criminals repeatedly doing so, but allowed facemasks due to theCOVID-19 pandemic.[75] In the2019–20 Hong Kong protests, some protestors wore surgical masks amongst other types of mask to avoid recognition, and the governmentbanned such use.[76]
Research carried out during the COVID-19 pandemic found that surgical masks increase the attractiveness of the wearer[77][78] and this is more so than other types of face coverings.[79]
Researchers are developing face-masks which may help reduce viral spread better than existing ones and/or have possibly useful properties such asbiodegradability or better breathability.[80][81][82][83][84][85][86] Some are exploring whether attachments could be added to existing face-masks to make them more effective[85] such as due to virus-deactivating fabrics or impregnations.[85][84] The COVID-19 pandemic increased efforts to develop such masks.[85]
There also is an experimental face mask with an embeddedbiosensor that can detect a pathogenic signature (such as one ofSARS-CoV-2)[87] and face masks that glow under ultraviolet light if they contain SARS-CoV-2 when the filter is taken out and sprayed with a fluorescent dye that contains antibodies from ostrich eggs.[88]
Other research investigated environmental pollution associated with face mask waste management[89][90][91] and weak spots of masks with product designs of the widely appliedFFP standards, in particular variants with exhalation valves.[92]
Surgical masks for use in the US and the EEA conform toASTM F2100[11] and EN 14683[9] respectively. In both standards, a mask must have aBacterial Filtration Efficiency (BFE) of more than 95%, for an aerosol of particles of size approximately 3.0 μm.[93]
In China, two types of masks are common: surgical masks that conform to YY 0469 standard (BFE ≥ 95%, PFE ≥ 30%, splash resistance) and single-use medical masks that conform to YY/T 0969 standard (BFE ≥ 95%).[39][94] Daily protective masks conforming to GB/T 32610 standard[95] is yet another type of masks that can have similar appearance to surgical masks.
In 2014, Firat Güder while he was a research fellow at Harvard University, together with Professor George Whitesides, invented a wireless surgical face mask that can monitor breathing of the individual wearing the mask. Their technology relied on disposal paper-based printed sensors which could be integrated into the mask.[96] The technology, which was first published in 2016, led to the formation of a start-up (Spyras Ltd) company to commercialize it which was later acquired.
^Skaria S, Smaldone G (2014). "Respiratory Source Control Using Surgical Masks With Nanofiber Media".Annals of Occupational Hygiene.6 (58):771–781.
^Li Y, Wong T, Chung J, Guo YP, Hu JY, Guan YT, et al. (December 2006). "In vivo protective performance of N95 respirator and surgical facemask".American Journal of Industrial Medicine.49 (12):1056–1065.doi:10.1002/ajim.20395.PMID17096360.
^MacIntyre CR, Chughtai AA (April 2015). "Facemasks for the prevention of infection in healthcare and community settings".BMJ.350 (apr09 1): h694.doi:10.1136/bmj.h694.PMID25858901.S2CID46366687.
^abTalic S, Shah S, Wild H, Gasevic D, Maharaj A, Ademi Z, Li X, Xu W, Mesa-Eguiagaray I, Rostron J, Theodoratou E, Zhang X, Motee A, Liew D, Ilic D (November 2021)."Effectiveness of public health measures in reducing the incidence of covid-19, SARS-CoV-2 transmission, and covid-19 mortality: systematic review and meta-analysis".BMJ.375 e068302.doi:10.1136/bmj-2021-068302.PMC9423125.PMID34789505.S2CID244271780.The results of additional studies that assessed mask wearing ... indicate a reduction in covid-19 incidence, SARS-CoV-2 transmission, and covid-19 mortality. Specifically, a natural experiment across 200 countries showed 45.7% fewer covid-19 related mortality in countries where mask-wearing was mandatory. Another natural experiment study in the US reported a 29% reduction in SARS-CoV-2 transmission (measured as the time-varying reproductive number Rt) (risk ratio 0.71, 95% confidence interval 0.58 to 0.75) in states where mask-wearing was mandatory. A comparative study in the Hong Kong Special Administrative Region reported a statistically significantly lower cumulative incidence of covid-19 associated with mask-wearing than in selected countries where mask-wearing was not mandatory.
^ab"Science Brief: Community Use of Masks to Control the Spread of SARS-CoV-2". CDC. 11 February 2020.Experimental and epidemiologic data support community masking to reduce the spread of SARS-CoV-2, including alpha and delta variants, among adults and children. [...] Mask use has been found to be safe and is not associated with clinically significant impacts on respiration or gas exchange under most circumstances, except for intense exercise. The limited available data indicate no clear evidence that masking impairs emotional or language development in children.[I]n combination with other contextual cues, masks are unlikely to produce serious impairments of children's social interactions. A study of 2-year-old children concluded that they were able to recognize familiar words presented without a mask and when hearing words through opaque masks. Among children with autism spectrum disorders (ASD), interventions including positive reinforcement and coaching caregivers to teach mask-wearing have improved participants' ability to wear a face mask. These findings suggest that even children who may have difficulty wearing a mask can do so effectively through targeted interventions.
^Koh XQ, Sng A, Chee JY, Sadovoy A, Luo P, Daniel D (February 2022). "Outward and inward protection efficiencies of different mask designs for different respiratory activities".Journal of Aerosol Science.160 105905.Bibcode:2022JAerS.16005905K.doi:10.1016/j.jaerosci.2021.105905.
^MacIntyre CR, Chughtai AA (April 2015). "Facemasks for the prevention of infection in healthcare and community settings".BMJ.350: h694.doi:10.1136/bmj.h694.PMID25858901.S2CID46366687.
^"CJCU Student Handbook"(PDF). 2016. Archived fromthe original(PDF) on 14 January 2020. Retrieved4 April 2020.In Taiwan, it is considered courteous to wear a face mask if you have a cold and cough and plan to be in close proximity with others
Chen, Chih-Chieh; Willeke, Klaus (1992). "Aerosol penetration through surgical masks".American Journal of Infection Control.20 (4):177–184.doi:10.1016/S0196-6553(05)80143-9.PMID1524265.
Comments on the previous paper; tests using aparticle counter instead of an Andersen sampler, and compares the results to30 CFR 11 NIOSH respirators
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