Mouth and nose protection

from Wikipedia, the free encyclopedia
Mandatory sign M016: Use mask
Mouth and nose protection with ties
Mouth and nose protection with elastic fixing straps

The mouth and nose protection ( MNS , also: mouth protection for short , other names: mouth and nose mask , surgical mask , medical face mask , clinic mask , surgical face mask or hygiene mask ) is a medical product with the purpose of transmitting pathogens through secretion droplets to reduce. A certified mouth-nose protection has a high filtration effect, so that when the mask is fitted correctly, the wearer of the mask is protected (self-protection), but in particular the emission of pathogens is significantly reduced (external protection). Details can be found in the Effectiveness section .

It is a medical half face mask that is attached to the back of the head or behind the ears with ties or elastic bands . As a rule, it consists of three layers of non-woven fabric , of which the middle layer absorbs the viruses and bacteria or the droplets that carry them due to its particularly fine fibers, which are usually produced using the meltblown process. In the two-layer mouth-nose masks, which are less common, the meltblown layer is on the outside. With an integrated, flexible metal bracket in the middle of the upper edge, the half mask is pressed against the bridge of the nose in order to keep the field of view free and to restrict the air inlet and outlet upwards.

Medical mouth and nose protection must meet different requirements for bacterial filter performance, differential pressure and germ load when not in use. If the breathing air is inhaled through the mouth and nose protection, the mouth and nose protection achieves a high filtration effect against virus-carrying aerosol particles and droplets. 0.1 µm particles are separated at least 95 or 98 percent (MNS type I or type II), with larger and smaller particles the separation rate is even better. If air flows past the mouth and nose mask when breathing, especially as a result of the mask being incorrectly fitted or incorrectly worn, the effectiveness of the mouth and nose mask is significantly reduced. Even when worn correctly, a small proportion of the air you breathe flows past the mask.

For this reason, FFP masks are to be distinguished from mouth and nose protection , the separation efficiency of which is comparable to that of certified mouth and nose masks, but which, due to the sealing of the mouth and nose, are better than mouth and nose protection against inhalation Microparticles protect because the inhaled air is prevented from flowing past, unlike mouth and nose protection.

Simple (self-made or non-standardized) paper or fabric masks, so-called everyday masks , which are not medical products and for which no such requirements are made, must also be clearly distinguished . In contrast to mouth and nose protection, the effect and the germ content of an everyday mask are accordingly of very different quality and cannot be easily determined. In the case of simple fabric masks, no filter effect against viruses or virus-carrying aerosols can be assumed, but these also develop external protection to a certain degree.

Everyday masks, mouth-nose masks and FFP masks belong to the group of protective masks . The article protective mask gives an overview of the requirements and the respective effectiveness of the different products.

Classification

As a medical product of risk class I according to the Medical Device Directive (93/42 / EEC, MDD), mouth and nose protection in the European Union must meet the European standard EN 14683: 2019-6 and also have a CE mark . It is part of personal protective equipment (PPE) in the health sector. After a single use, the MNS should be disposed of; It may only be reused in exceptional cases after appropriate decontamination (see the section on exemptions in Germany ).

According to the norm, mouth-nose masks are divided into different types (I, II and IIR) depending on their filtration effect; Type IIR corresponds to type II with additional requirements for fluid resistance.

Type I masks have a bacterial filter performance (BFE) of at least 95%, type II and II R at least 98%. The breathing resistance for masks type I and II must be less than 40  Pa / cm², for type IIR less than 60 Pa / cm². Liquid-resistant Type IIR masks must withstand an injection pressure of at least 16 kPa. To ensure that the masks do not pose a microbial risk to the wearer or the patient, a limit value for the germ load of the as yet unused product has been set at a maximum of 30 CFU / g for all types .

There is also the US specification according to ASTM F2101. This standard also divides mouth and nose protection into three classes (level 1 to level 3). The requirements for bacterial filter performance are identical to the European standard (95% for level 1, 98% for level 2 and 3); In addition, according to ASTM F2101, the masks must also separate 0.1 µm synthetic particles with the same performance. The requirements for breathing resistance are less strict in the US standard than in the European standard; for the masks to ASTM F2101 have low flammability be ( Flame Class 1).

Masks according to DIN EN 14683, ASTM F2101 or equivalent specifications are designated as medical masks by the World Health Organization .

Self-made makeshift masks made of commercially available materials for private use in everyday life ( everyday masks ) are not considered a medical product or part of personal protective equipment. You are not allowed to replace professional masks in places where they are mandatory.

Manufacturing

Professional mouth and nose masks are typically made of non-woven fabric . They are usually designed in three layers as "SMS" laminates. This means that the two outer layers of fleece are spunbond materials and the layer in between is a fleece that has been manufactured using the meltblown process. The nonwovens are manufactured in an upstream process. The meltblown fleece layer in between consists of extremely small, randomly laid fibers that give the mask the required separation efficiency (see the section on classification ).

The production of mouth and nose masks takes place on semi to fully automatic production machines. To do this, the three layers of non-woven fabric and a wire that serves as a nose clip are first fed in, whereby the non-woven fabric is usually folded three times in the middle. When using the mouth and nose mask, this enables the mask to be enlarged along the body axis, as a result of which the mask can be pulled over the chin of the wearer. The fleece layers are firmly connected to one another via welding (usually by ultrasonic welding ) and the nose clips are integrated into the fleece layers. Finally, the fleece is cut at regular intervals, creating the individual masks. In the last step, ear or head straps are attached - often also by ultrasonic welding, although other joining methods such as gluing can also be used.

Until the beginning of 2020, mouth and nose masks were almost exclusively manufactured in Asia; The necessary meltblown fleece was also a niche product in Europe . In Germany, until March 2020, there was no production facility for mouth and nose masks that were certified as medical devices. There was no such production in the United States either. With the spread of the COVID-19 pandemic in Germany and the associated material shortage, the German federal government commissioned a total of 50 companies in Germany with the construction of corresponding production facilities, assured subsidies and guaranteed the acceptance of the products until at least the end of 2021. The goal is the distribution of 40 million surgical masks per week throughout Germany from August 2020. According to media reports, however, many of these companies failed to get the masks approved, especially because of the requirements for obtaining the CE mark .

German companies that started producing surgical masks in 2020 include Hengst Filtration , Schiesser , Bugatti , Sandler AG and Melitta .

Functionality and effectiveness

A dentist wears mouth and nose protection (internal and external protection) as well as protective goggles (internal protection only).
Version bound from a cheesecloth

Since the mucous membranes of the eyes, mouth and nose are potential entry points for pathogens, mouth and nose protection during treatment, care or examination can protect the patient from microorganisms from the oropharynx of employees that are emitted when speaking and coughing become. Conversely, mouth and nose protection protects staff from splashing body secretions or contaminated liquids and from touching their mouth and nose with contaminated hands. In some cases, staff also wear protective goggles or visors to protect their eyes , for example when caring for patients with an influenza infection or during an operation.

effectiveness

Effect of sneezing without a face mask
With the help of streak photography , the effect of various barriers on the breathing flow when sneezing can be visualized

Wearing close-fitting, multi-layered and not moistened mouth-nose protection can reduce the likelihood of droplet infection in close proximity to potentially infected persons by preventing liquid particles from reaching the mucous membranes or the airways when breathing, speaking, sneezing or coughing . The mouth and nose protection can thus reduce the direct germ load, but in the medical environment, especially in closed rooms, it is not a sufficient protection against infection on its own , since "depending on the location of the MNS, the wearer essentially does not inhale through the fleece of the MNS, but the breathing air is sucked in past the edges of the MNS ”.

The materials of the mouth and nose protection can only filter part of the bioaerosols from the direct exhaled air of the wearer and the particles bound to them in the droplets and this only as long as the fleece is sufficiently dry.

Although the effectiveness of mouth and nose protection as a hygiene measure is hardly questioned, the data situation with randomized comparative studies that prove this statistically unequivocally was rather poor until recently.

A study published in April 2020 has since shown that even simple protective masks can effectively reduce the release of viruses (such as the influenza or SARS-CoV-2 virus) through droplets and aerosols .

An experimental study commissioned by the Dutch Ministry of Health also came to the conclusion in 2008 that any type of mouth and nose protection, even if the fit was insufficient or improvised material, reduced aerosol exposure. Especially when speaking, the risk of droplet infection can be effectively reduced and is therefore a useful addition to the other hygiene measures.

In addition to external protection, there is also a self-protection effect for mouth and nose masks that meet the requirements of EN 14683: 2019 (see section classification ). While the same level of protection not like a FFP2 - respirator can be achieved, also a full-face protection on the one hand the impact prevents macroscopic droplets onto the mouth and nasal mucosa of the carrier and on the other hand in a position, a large part of the aerosol droplets, the Viruses and bacteria contribute to filtering. A type I mouth and nose mask must filter at least 95 percent, a type II mask at least 98 percent of these droplets and thus significantly reduce the viral load of the inhaled air. In contrast to the FFP2 respirator, however, this effect may be considerably reduced by air flowing past the mask at the side.

In addition to reducing the viral load of the inhaled air, mouth and nose protection can protect the face area from contact with contaminated hands.

A study by the University of the Federal Armed Forces in Munich has shown - according to its own statements, "not strictly scientific" - experiments that the desired protective effect of many masks is inadequate and that these do not achieve the desired protective effect. In part, the study suggests that inappropriate use can lead to higher infection rates.

With Schlieren photography can be made visible, like wearing a full-face protection, the currents slows the breathing air (see video at right).

Areas of application

Use of mouth and nose protection in Calcutta in 1944

Clean rooms

In clean rooms in medicine and pharmacology, for example for the preparation of sterile goods or the cultivation of bacteria , mouth and nose protection is often used so that no secretion droplets get onto surfaces and cultures that have to be kept clean, which would otherwise falsify the measurement result.

In production facilities for semiconductor production, they prevent salt crystals from the air you breathe from reaching the wafers and doping the semiconductor .

Operating rooms

During operations on non-infectious patients, standardized MNS masks prevent drops from the surgeon's nose or mouth from dripping into the operating area and inadvertently contaminating it. The surgeon's potentially contaminated breathing air that flows around the mask is not a problem here because it is kept away from the patient by means of a clean air system above the operating table.

When performing operations on infectious patients, the surgeon wears a full face mask in addition to the MNS to protect himself. Even with outpatient operations or sampling of infectious tissue z. B. Excisions , a MNS is also strongly recommended.

The Commission for Hospital Hygiene and Infection Prevention (KRINKO) demands that the mouth and nose protection in the operating area is sufficiently large to cover the mouth and nose. It must lie close to the face and the whiskers must be completely covered. It should be put on with previously disinfected hands before entering the operating room if “the sterile instruments have already been set up, an operation is about to begin or an operation is being carried out”. The MNS should be renewed before every operation, if there is visible contamination or moisture penetration or after two hours at the latest; Hygienic hand disinfection must be carried out after changing the mask .

Use in public as a preventive measure

In Asia it is considered an act of politeness to wear a mask when sick; however, mouth and nose protection is also used because of air pollution.

FFP masks with exhalation valves are no alternative to mouth and nose protection if external protection is required against the transmission of pathogens through secretion droplets and as it has been prescribed nationwide in closed public spaces since April 27, 2020. In its current risk information, the Federal Institute for Drugs and Medical Devices expressly warns against use: "Masks with a valve only filter the inhaled air and are therefore not designed for external protection." Healthcare workers should wear such FFP masks with a valve during activities Reserved for patients suspected of COVID-19.

  • A passenger without a face mask was denied boarding during the 1918 Spanish flu in Seattle

  • At the same time, police officers wear face masks across the board

  • In Asia, wearing mouthguards in public is widespread

  • A US soldier during a " dirty bomb " response exercise (June 2011)

COVID-19

Use of surgical masks at a press conference by Jair Bolsonaro on the corona crisis (March 2020)

The COVID-19 disease is characterized by an incubation period of an average of 5 to 6 days , in individual cases up to 14 days. Occasionally, infected people develop symptoms within 24 hours. Some people can already be infectious during the incubation period, even before they show symptoms (see also COVID-19 # transmission path ). In this context, therefore, the wearing of masks - although in most cases no statement is made about which type of protective mask is meant - is discussed in public even without any recognizable signs of illness. In Asia, in particular, where the wearing of protective masks was already widespread in public, many countries quickly introduced a general mask requirement . In March 2020, doctors from Hong Kong recommended introducing this practice in other countries as part of the COVID-19 pandemic based on positive experience. The virologist Alexander Kekulé also suspects that the widespread wearing of protective masks there could prevent a worse outbreak, and therefore recommended that the population (and especially employees with a lot of personal contact) always wear mouth and nose protection in public - also, if it were just simple masks.

A current publication from May 2020 again emphasizes the importance of the face mask in reducing the spread of SARS-CoV-2.

Since the COVID-19 pandemic led to delivery bottlenecks in infection protection materials and these should also preferably be left to clinics and other facilities, there are increasing numbers of instructions for self-made makeshift mouth and nose masks ( everyday masks , community masks). But may not Behelfsmasken "as commercial medical products or objects personal protective equipment placed on the market and not with corresponding benefits or protective effects awarded are" but to be used exclusively in the private (non-medical) environment.

Unsuitable areas of application for MNS

Since mouth-nose protection does not adequately protect against very fine particles and gases, it is not suitable for use to reduce pollen or dust pollution of the respiratory tract, during construction and renovation work, in the event of severe air pollution (e.g. during a so-called " haze. " “), Or for civil protection purposes (for example in the event of fire or accidents involving dangerous goods ). For such purposes, fine dust masks , special respiratory masks or smoke protection hoods of classes FFP1 to FFP3 (“ particle filtering half mask ”) are recommended.

When treating quarantined patients with highly infectious diseases such as overt tuberculosis or measles, one MNS is not enough. In these cases, at least a class FFP2 respirator should be worn; complete, tightly fitting protective equipment is required on special isolation wards .

Application and reusability

The Federal Institute for Drugs and Medical Devices has issued recommendations for the use of medical mouth and nose protection in Germany , according to which hands should be washed thoroughly before putting on the mask, in order not to contaminate the inside in particular . The mask should completely cover the mouth and nose and be as close as possible to the edges "to minimize air penetration at the sides". In addition, the outside of the mask should not be touched when it is worn, as it is considered to be potentially pathogenic. Hands should be washed again after removing the mask. A moistened mask should be removed immediately and replaced if necessary.

As a rule, mouth and nose protection must be disposed of as a single-use item after use.

Derogation in Germany

This paragraph shows the situation in Germany . Help us to describe the situation in other countries.

In connection with the COVID-19 pandemic in Germany , delivery bottlenecks arose, so that the Robert Koch Institute (RKI) has an option for the resource-saving use of mouth and nose protection (MNS) and FFP respirators, which is temporarily valid until August 31, 2020 prepared in health care facilities, in coordination with the ad hoc working group on SARS-CoV-2 of the Committee for Biological Agents (ABAS) and in cooperation with the Federal Ministry of Labor and Social Affairs (BMAS): According to the submission of the BMAS and the Federal Ministry of Health (BMG) for the federal government's crisis team from March 31, 2020, MNS can be reused for the purpose of external protection in everyday ward life, in outpatient clinics or care facilities without decontamination; This requires a personalized commitment. Re-use is excluded for use in the operating theater or for interventional procedures . In addition, the exemption was limited to a maximum of six months.

Accordingly, there is the possibility of reusing MNS and FFP masks in "declared emergency situations" under certain conditions. What is necessary in advance is a "competent risk assessment or risk assessment by the employer on site, taking into account the local conditions, including the hygiene staff, the company medical service and, if necessary, in consultation with the responsible health department." Safe handling is necessary to avoid the risk of infection for employees to keep it low. The following measures apply, among others:

  • An MNS may only be reused during a shift by the same person and in a patient-specific manner, but not “after activities on infectious patients with pronounced exposure to aerosols ”, as it is e.g. B. arise during a bronchoscopy or when suctioning the airways.
  • The MNS must be changed immediately in the event of - even suspected - contamination or moisture penetration.
  • When stopping the MNS, contamination of the MNS (especially the inside) or contamination of the face should be prevented.
  • After it has been put down, the MNS should be stored in a dry place in the open air in a storage area that is not accessible to the public; without contamination of the inside of the MNS or spreading to other surfaces.
  • The used MNS must be clearly assigned to a person (e.g. by marking the mask) in order to prevent it from being worn by other people
  • Before putting the MNS back on, make sure that the inside of the filter fleece is not touched to prevent the pathogens from spreading from the contaminated outer surface to the inner surface.
  • The place where the temporary storage took place must be properly disinfected immediately after the MNS has been removed.

decontamination

To decontaminate mouth and nose protection, temporary heat inactivation using dry heat at 65 to 70 ° C for 30 minutes was recommended. In May, the Federal Ministry of Health's respiratory protection team declared that the procedure described could no longer be recommended. A higher temperature and a longer time may be necessary.

Linguistic development

On July 5, 2020, the term Snutdauk based on Schnutentuch was chosen as the most beautiful new creation in the Low German competition . The term comes from the word family of the Snutenpulli with the meaning of mouth protection or mouth and nose covering according to the Fritz Reuter Literature Museum Stavenhagen ( Mecklenburg-Western Pomerania ).

literature

  • Feng, Shuo & Shen, Chen & Xia, Nan & Song, Wei & Fan, Mengzhen & Cowling, Benjamin. (2020). Rational use of face masks in the COVID-19 pandemic. The Lancet Respiratory Medicine. 10.1016 / S2213-2600 (20) 30134-X.

Web links

Commons : Mouthguard (Medicine)  - Collection of images, videos and audio files
Wiktionary: mouthguard  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ a b c d e f BfArM - Recommendations of the BfArM - Instructions from the BfArM on the use of self-made masks (so-called "community masks"), medical mouth and nose protection (MNS) and filtering half masks (FFP2 and FFP3) im Connection with the coronavirus (SARS-CoV-2 / Covid-19). Retrieved April 3, 2020 .
  2. ↑ a b Information sheet EN 14683: 2019. Medical face masks - requirements and test methods. Dach-germany.de; accessed on April 19, 2020
  3. ↑ EN14683 Harmonizes Bacterial Filtration Efficiency and Differential Pressure with ASTM F2100. Nelson Labs , 2014, accessed June 13, 2020 .
  4. ↑ Advice on the use of masks in the context of COVID-19. (PDF) WHO , June 5, 2020, p. 2 , accessed June 13, 2020 .
  5. ↑ Video of a mask production line , Via Automation
  6. ↑ Video of a mask production , KYD Automatic Mask Machine Factory
  7. ^ A b Nele Husmann: Mask production in Troisdorf: Here the head of state buys personally. Wirtschaftswoche , accessed on June 14, 2020 .
  8. ↑ Basic material for FFP masks: How Innovatec deals with run on "Meltblown". manager magazin , accessed on June 14, 2020 .
  9. ↑ a b masks made in Germany: How is production going in this country? Editorial network Germany , accessed on June 14, 2020 .
  10. ↑ Benedikt Becker, Nele Husmann, Thomas Kuhn, Thomas Stölzel: Protective clothing: The would-be mask makers. Wirtschaftswoche , accessed on June 14, 2020 .
  11. ↑ a b Infection prevention as part of the care and treatment of patients with communicable diseases. Bundesgesundheitsblatt 2015, 58: 1151–1170 DOI 10.1007 / s00103-015-2234-2, p. 1154 ; accessed on March 5, 2019
  12. ↑ EN 14683; accessed on March 26, 2020
  13. ↑ a b Overview of infectious diseases and required measures as a basis for stipulations in the hygiene plan. KRINKO 2016 ; accessed on March 7, 2019
  14. ↑ S. Dreller et al .: On the question of suitable respiratory protection for airborne infections. 2006; accessed on April 6, 2020
  15. ↑ Jörg Blech, Matthias Gebauer, Kristina Gnirke, Julia Amalia Heyer, Christoph Hickmann, Christiane Hoffmann , Nils Klawitter, Martin U. Müller , Cornelia Schmergal, Christoph Schult: That's why Germany has a mask problem - DER SPIEGEL - Politics. In: Der Spiegel . Retrieved April 4, 2020 .
  16. ^ Nancy HL Leung, Daniel KW Chu, Eunice YC Shiu, Kwok-Hung Chan, James J. McDevitt: Respiratory virus shedding in exhaled breath and efficacy of face masks . In: Nature Medicine . April 3, 2020, ISSN  1546-170X , p. 1–5 , doi : 10.1038 / s41591-020-0843-2 ( nature.com [accessed April 3, 2020]).
  17. ^ Marianne van der Sande, Peter Teunis, Rob Sabel: Professional and Home-Made Face Masks Reduce Exposure to Respiratory Infections among the General Population. PLOS ONE, July 9, 2008, doi: 10.1371 / journal.pone.0002618 ; accessed on March 23, 2020.
  18. ↑ Covid-19: Protection against infection. In: Lungenaerzte-im-Netz. Retrieved March 27, 2020 .
  19. ^ Christian Jassoy, Andreas Schwarzkopf: Hygiene, Infectiology, Microbiology. Thieme, Stuttgart 2018, p. 33, ISBN 978-3-13-241368-9 .
  20. ↑ a b Resolution 609 Occupational Health and Safety in the event of human influenza that is not sufficiently preventable from vaccination. Decision of the Committee for Biological Agents, June 2012 edition, Annex 2; accessed on March 23, 2020.
  21. ↑ Christian J. Kähler, Rainer Hain: Flow analyzes for the SARS-CoV-2 protective mask debate . As of April 11, 2020; accessed on April 30, 2020.
  22. ↑ Conrad Völker, Dana Höftmann, Amayu Wakoya Gena: Keeping your distance: New video from the Bauhaus University Weimar shows how air spreads. In: Bauhaus University Weimar . Professorship of Building Physics, March 20, 2020, accessed on April 7, 2020 .
  23. ↑ Hygiene tip of the DGKH, September 2011: Mouth and nose protection. German Society for Hospital Hygiene eV ; accessed on March 5, 2019
  24. ↑ Prevention of post-operative wound infections. Recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute, 2018, p. 461; accessed on April 15, 2020
  25. ↑ Covid-19: Hygiene and other protective measures. Protection against infection. Lungenaerzte-im-netz.de, section mouth protection ; accessed on April 11, 2020
  26. ↑ https://www.bfarm.de/SharedDocs/Risikoinformationen/Medizinprodukte/DE/schutzmasken.html
  27. ↑ Recommendations of the BAuA on the use of protective masks in connection with SARS-CoV-2. Status: April 3, 2020; accessed on April 27, 2020.
  28. ↑ Advice on the use of masks in the community, during home care and in healthcare settings in the context of the novel coronavirus (COVID-19) outbreak. Accessed April 10, 2020 (English).
  29. ↑ Chi Chiu Leung: Mass masking in the COVID-19 epidemic: people need guidance. Lancet, March 3, 2020, doi: 10.1016 / S0140-6736 (20) 30520-1
  30. ↑ Alexander Kekulé: Coronavirus: Ways out of lockdown . In: The time . March 26, 2020, ISSN  0044-2070 ( zeit.de [accessed on March 27, 2020]).
  31. ↑ https://www.prosieben.de/tv/prosieben-live-deutschland-fragt-zu-corona/video/20201-experten-beantwort-eure-fragen-zu-corona-sendung-vom-25-maerz-ganze -episode
  32. ↑ Kimberly A. Prather, Chia C. Wang, Robert T. Schooley and others: Reducing transmission of SARS-CoV-2. DOI: 10.1126 / science.abc6197. In: Science. May 27, 2020, accessed May 31, 2020 .
  33. ↑ Possible measures for the resource-saving use of mouth and nose protection (MNS) and FFP masks in healthcare facilities in the event of delivery bottlenecks in connection with the novel coronavirus disease COVID-19. RKI, as of March 13, 2020; accessed on March 23, 2020.
  34. ↑ Sew mouthguards yourself - that's how it works! Mdr.de; accessed on March 23, 2020
  35. ↑ Recommendations of the Swiss Federal Office of Public Health , status: 2018; accessed on April 6, 2020
  36. ↑ Coronavirus disease (COVID-19) advice for the public: When and how to use masks. WHO.int; accessed on April 6, 2020
  37. ↑ a b Possible measures for the resource-saving use of mouth and nose protection (MNS) and FFP masks in healthcare facilities in the event of delivery bottlenecks in connection with the novel coronavirus disease COVID-19. RKI, as of March 14, 2020; accessed on April 15, 2020.
  38. ↑ Use of protective masks in health care facilities - paper of the Federal Government's crisis team from March 31, 2020.
  39. ↑ Secure supply with respiratory masks. Note dated May 7, 2020: reuse of respirators. Press release of the BMG's crisis team respiratory protection masks; accessed on May 19, 2020
  40. ↑ https://www.aerzteblatt.de/nachrichten/112416/Bisher-empfenken-Maskenaufnahm-toetet-SARS-CoV-2-nicht-ab
  41. ↑ "Snutdauk" means "mouthguard": Low German new creation
  42. ↑ This is the Low German word for mouthguard