Elastomeric respirator

Protective P100 half-face elastomeric filter mask worn by a NYPD officer; proprietary 3M pink pancake filters
Similar mask with generic flat disk filters.

Elastomeric respirators, also called reusable air-purifying respirators,[1] are a type of respirator that seals to the face using a mask made of an elastomeric material, which may be a natural or synthetic rubber. They are generally reusable. Full-face versions of elastomeric respirators seal better and protect the eyes.[2]

Elastomeric respirators consist of a reusable mask that seals to the face, with exchangeable filters.[3][4] Elastomeric respirators can be used with chemical cartridge filters that remove gases, mechanical filters that retain particulate matter, or both.[5] As particulate filters, they are comparable[3] (or, due to the quality and error-tolerance of the elastomeric seal, possibly superior[6]) to filtering facepiece respirators such as N95 respirators and FFP masks.[3]

Elastomeric air-purifying respirators are reusable because the facepiece is cleaned and reused, but the filters are discarded and replaced when they become unsuitable for further use.[4] Some, but not all, filter materials are proprietary and manufacturer-specific,[7] and supply-chain failures can make replacements hard to find.[2][7]

Although powered air-purifying respirators and air-supplying respirators may have elastomeric masks, they are not generally referred to as elastomeric respirators.[3][4]

Physical form

This full-face mask also protects the eyes, and has an inner orinasal mask to reduce dead space. Pink hard-case P100 particulate filter cartridges make their presence or absence conspicuous at a distance.

Elastomeric respirators are examples of air-filtering respirators, in contrast to air-supplying respirators. Air-supplying respirators are usually positive-pressure, so they leak outwards, and thus offer better protection. They are more complex and heavier, but less bulky about the head, and can be worn for longer.[1] Air-purifying respirators draw the surrounding air through filters which remove contaminants.[8]

A range of elastomers are used, including silicone, neoprene, EPDM (ethylene propylene diene monomer rubber), or proprietary elastomers such as Hycar. Latex is rarely used due to allergies. Many manufacturers offer a choice of two materials.[6]

Elastomeric respirators include:[9]

  • mouth-bit respirators, which fit in the mouth with the nose pinched shut (escape only)
  • quarter-mask or orinasal mask, covering the mouth and nose only
  • half-mask, from below the eyes to below the chin
  • fullface mask, from above the eyes to below the chin

Some elastomeric masks include one-way valves to let exhaled air out unfiltered. This reduces the resistance when the user is breathing out, and some find it makes the mask more comfortable.[2] It may also reduce inwards leakage.[10] However, masks which do not filter exhaled air cannot be used for source control.[2]

Filter types

An exploded view of a respirator, showing two reusable plastic screw-on rings and a disposable disk of N95 particulate filter material.
Disk of filter material from previous image, with mark showing it is N95-certified circled
Another type of filter disk. This is a P100 filter, a higher standard than the previous N95 filter.

Air-purifying respirators have filters. The masks and filters come in a variety of standards for mechanical filters and for chemical cartridges, intended for a variety of purposes.[8] An appropriate standard of filter must be used for the mask to be effective.[2]

Filters may be contained in cartridges or canisters; there are also flexible flat and pancake-style filters (see illustrations).[2] Filters are usually mounted on the face, but in the case of powered air-purifying respirators, they are mounted on the belt, and a fan drives air through them and into the face mask. Most masks take one or more filters.[6]

Particulate filters

As of 2020, the commercially available particulate filter disks and cartridges are disposable, and must be replaced when clogged due to accumulated particles (so that breathing resistance is too high), damaged (torn or soiled with something that will damage the filter, such as many fluids; physical or chemical damage), or contaminated (the outside has caught dangerous particulates; for instance, infectious particles).[2] Disinfection and reuse techniques have been tested for emergency use; some, like soap and water, destroy traditional disposable electret filters by removing the electret charge. Launderable, reusable electret filters were being developed during the COVID-19 pandemic.[10]

Particulate filters may be simple disks or other shapes of flat filter material,[11] which are lightweight,[12] or they may be pancake-style[2] hollow discs with a smaller central plastic connecting tube on one side.[13] Particulate filters may also be enclosed in hard-cased disposable cartridges. The disposable cases protect the filter against splashes and can be wiped clean, which may be important in some applications.[14][2]

In the 2020 COVID-19 pandemic, plastic adapters and filter-holders were 3D-printed in large quantities. These fit on common masks originally made to take proprietary filters (the type shown below). The adapters hold circles cut out of surgical masks, utilizing them as filter discs (as shown above). Six filter discs can be cut from one mask.[15]

Like other proprietary refills, proprietary filter cartridges cause vendor lock-in.

Chemical cartridges

A protester in Venezuela wearing a gas mask, an elastomeric respirator with chemical cartridges.
The manufacturer-specific cartridge filter. Colour-coding suggests that this brown-banded cartridge is a different standard from the yellow-banded cartridges the protestor is using.

Different types of cartridge must be used to filter out different chemicals. Most cartridges are made of activated charcoal, which has a very high surface area to adsorb toxins onto. These carbon filters are often impregnated with reagents which react and bond with the specific airborne chemical(s) the cartridge targets. This process is called chemisorption; the reagents bond the toxic gases and vapors before the wearer can breathe them in. The activated carbon may be saturated with copper, zinc, silver and molybdenum compounds, as well as with triethylenediamine (TEDA)[16][17] Many chemicals cannot be safely filtered out by any chemical cartridge.[18]

Chemical cartridges must generally be kept sealed from the air until use, and will eventually be too old to use even if kept sealed.[19]

Many chemicals bond to the cartridge material fairly irreversibly, through chemisorption.[17] But some adsorbed organic vapours may only bond weakly and reversibly (for example methanol[20]). These organic vapours, especially the more volatile ones, may desorb from the filter and diffuse through the cartridge while it is not in use, such that they may be breathed by the wearer when they begin to use the cartridge again.[21][18] For this reason, cartridges used against organic vapours are single-use, unless experimental evidence shows that desorbtion-caused breakthrough after a storage period is not a problem for the specific organic vapours in question.[22][18]

Chemical cartridges must be replaced when they no longer have the ability to absorb the toxic chemicals, a point which is determined by a qualified industrial hygienist. Cartridge service life is dependent on many factors,[6][22] including contaminant type and concentrations, interference from other chemicals, breathing rates, whether respirator use is continuous or intermittent, sorption capacity of the cartridges, and environmental factors like humidity and temperature.[23] There is active research into making more types of chemical cartridge with an end-of-service-life indicator (ESLI), which indicates to the user when the cartridge has expired.[24][21][23] ESLIs may be moisture-dependent, in which case relying on them for use in dry atmospheres could cause dangerously high exposures.[23]

Traits

Use of respirators in the workplace; see minutes 6:47-8:20 for elastomeric respirators, and 10:10-14:30 for filter types.

Air-purifying respirators cannot be used in oxygen-deficient atmospheres (less than 19.5% oxygen). Nor can they be used in atmospheres with a contaminant concentration that may be immediately dangerous to life or health, or in unknown atmospheres. In these cases air-supplying respirators must be used. If concentrations of hazardous particulates or gasses that are greater than the occupational exposure limit, U.S. regulations require that respirators be worn, but they may also be worn at lower concentrations.[25] Similar mandatory legal requirements apply to employers in many other countries (examples[26][27][28][29]). The respirator must have a sufficient assigned protection factor (APF) for the conditions.[25]

Respirators are rated by APF;[30] higher APFs protect more
TypeAPFprotects from
Disposable filtering facepiece respirators10[25][1]particulates only
Half-mask elastomeric respirators10[25][1]both particulates and gasses
Full-face-mask elastomeric respirators50[25][1]both particulates and gasses
Loose-hood PAPRs25 or 50[25][1][31]both particulates and gasses
Elastomeric PAPRs1000[31]both particulates and gasses
Supplied-air respirators (SARs)10-2000[25][1]both particulates and gasses
Self-contained breathing apparatus (SCBAs)50-10 000[25][1]both particulates and gasses

Elastomeric masks may fail to protect if they are not donned before investigating a funny smell. They will not protect if they are kept far away or in fiddly packaging so that they can not be donned within a single breath when a problem occurs. They will not protect if the user, without practice in being unable to breathe, panics and attempts to run rather than don the respirator. Other problems include using a size other than the size the wearer was fit-tested on, using the wrong sort of cartridge, re-using a cartridge that is no longer good, not doing a positive- and negative-pressure seal check each time the mask is donned, failing to test the respirator (and perhaps inhaling the carbon from a broken cartridge), and even putting the nose-clip up the nose rather than using it to pinch the nose shut.[32]

Fit

A CDC guide to facial hair and respirators
Mask-compatible eyeglasses, with flat elastomeric straps, to avoid interfering with the seal
Elastomeric full-face masks being worn with standard eyeglasses.

Fit is critical to the protection provided by elastomeric respirators. Elastomeric masks must be individually fit-tested and inspected for full efficacy.[2] They may be somewhat easier to fit than filtering facepiece respirators. Older mask designs were designed only to fit young adult men of average weight and a narrow range of ethnicities; newer ones use updated anthropometry and fit more people.[6]

Limited research suggests that elastomeric respirators may have better fitting characteristics than disposable filtering-facepiece respirators, fitting a broader variety of faces, and thus being more likely to seal well when the user has not done a formal fit test. Available evidence also suggests that as a class, elastomeric respirators may leak less, and their seals are less likely to become damaged. Elastomeric respirators have wider straps which slip less, individually-adjustable straps, and wider, softer, more flexible seals (see image below); these may help reduce leaks.[6]

Full-face elastomeric respirators generally seal better.[2] For substances hazardous to the eyes, a respirator equipped with a full facepiece, helmet, or hood is recommended.[25]

Eyeglasses can clash with elastomeric masks. Conventionally, full-face masks are modified, with prescription lenses inserted into the mask. Glasses can be worn over a half-mask, as long as they do not interfere with the seal or headstraps. Some users find this uncomfortable.[2][6] Wearing contacts is not possible where there is a risk of solvent vapours, and may not be advisable if there is an infection risk,[2] but otherwise contacts can be worn.[6]

Facial hair underneath the seal is also a problem. Piercings, jewelry, heavy cosmetics, and some creases and scars can also interfere with sealing.[6]

Straps may stretch slightly over time on some models.[6]

Communication

Left, Communicating with gestures, in a Russian hospital treating COVID-19 cases. Right, inside a Swiss military respirator, internal mask removed (replaced). The shiny metal shields a membrane for transmitting sounds. The item under the chin is an exhalation valve. The filter is attached to a third port between them, not visible here (outside view).[33]

It is harder to understand the speech of someone wearing most types of elastomeric respirator. This can be dangerous in some environments. Some commercially available respirators include sound-transmitting diaphragms and/or transparent windows giving a view of the mouth, to improve communication efficiency. Designs that allow the jaw to move more freely may also help. Electronic voice relays, from inside the mask or from a throat microphone, have also been used.[6]

Elastomeric respirators without these modifications muffle the wearer's speech more than filtering facepiece respirators (FFRs) such as N95 respirators. In some studies, this was a major reason why healthcare workers preferred to wear FFRs.[6]

Comfort

Many air-purifying respirators without air supply provide the workers with clean (purified) air with an excessively high concentration of carbon dioxide. For example, in the U.S. the permissible exposure limit for CO2 is 9 g/m3 (0.5% by volume) over an 8-hour shift, and 27 g/m3 (1.4% by volume) over any 15 minute period.[34] But values measured for elastomeric respirators can increase to 2.6%.[35] There is a lack of studies on the oxygen and carbon dioxide levels in the dead space behind an elastomeric respirator, but this may also cause headaches, especially if worn continuously for over 4 hours.[6]

Sweat does not evaporate as easily from under a mask; elastomeric respirators may be more hot and humid than FFRs. Heavier respirators cause more fatigue. More breathing resistance causes more fatigue, and makes the wearer more likely to feel out-of-breath or claustrophobic. Tight straps, on any type of respirator, are reported to put pressure on the sinuses and cause headaches.[6]

Uses

Firefighters testing elastomeric respirators, for light use in non-oxygen-deficient environments
Elastomeric masks are part of the equipment worn in mining
Making logs from rice chaff

First responders may use elastomeric respirators, including during smoke simulation exercises.[6]: Table2-1  Air-purifying respirators are not effective during firefighting, in oxygen-deficient atmosphere, or in an unknown atmosphere; in these situations an air-supplying respirator such as a self-contained breathing apparatus is recommended instead.[25]

Gas masks are extensively used in mining and construction. They are used against paint vapors, solvents, silica dust, and other hazardous particles and gasses.[6] Masons and carpenters use them against dusts and adhesives.[6]: Table2-1 

Elastomeric respirators may be used to protect against welding fumes.[36][6]: Box2-1  Different welding processes may produce different fumes, both particles and gasses such as carbon monoxide. Oxygen displacement by otherwise-harmless shielding gasses is also a risk.[37][38] A self-contained breathing apparatus may be needed.[36] Respirators used by welders must fit under a welding mask.[39]

Respirators are also used in demolition to protect against asbestos, mould, and other hazardous waste.[40]

Elastomeric respirators are used for cleaning up after oil spills.[41]

Elastomeric respirators are used against chemical aerosols and toxic gases.[6] They are used in the chemical industry when handling hazardous materials; workers are usually issued escape respirators as a precaution against leaks. Workers are instructed to put their mask on and leave immediately to sound the alarm if they detect a leak. Other respirators may be used for making repairs to leaking equipment.[32]

Elastomeric respirators may be worn in agriculture,[6]: fig.2–4  for instance when using agricultural chemicals, solvents, fish meal, silage, mold spores and dust.[42]

Manufacturing also uses elastomeric respirators,[6]: fig.2–4  for instance on assembly lines.[6]: Table2-1  Elastomeric respirators are worn by many employees in the nuclear industry.[6]

Medical use

A CDC video on the use of elastomeric respirators in healthcare

Elastomeric respirators have historically rarely been used in medicine, though this may change; the possibility of wider use was being investigated in the US in 2017.[30] Elastomeric respirators were used as a substitute for N95 respirators among shortages during the 2020 COVID-19 pandemic.[2] In medical use, the elastomeric portions of the mask must also be cleaned and disinfected, as some germs can survive on them for weeks. Conventionally, the filter cartridges are discarded.[2]

Filter cartridges can be hard to find amidst shortages. In emergency situations, if the filters are unclogged and unsoiled but contaminated with germs, the filters could be sterilized and re-used, although the filtration efficiency may be degraded by some forms of disinfection.[2] As of 2020, the available filter materials would be damaged by being dipped or submerged in cleaning fluid, but the outside of the filter cartridges can be cleaned and disinfected by wipes (pancake-style filters cannot be disinfected).[2] During the COVID-19 pandemic, public health authorities issued guidelines on how to save, disinfect and reuse standard mechanical filters, warning against the disinfection methods that damaged filtration efficiency.[43][44]

Limited research failed to find evidence that elastomeric respirators caused more patient anxiety than FFR masks, including in children and disoriented patients.[6] A single air-filtering elastomeric respirator cost about as much as 40 disposable filtering facepiece respirators, and a medical worker uses about 20 disposable masks per day, according to a 2018 publication. The particulate cartridges cost about as much as six disposable masks.[45] Air-supplying respirators may be easier for hospital personnel to use; they can be worn for longer periods.[1]

Source control

Elastomeric respirators with one-way valves that release unfiltered exhaled air are not recommended in disease-control settings where the unfiltered exhaled air might infect others, but can be used in some other settings.[2] In pandemics, masks with exhalation valves may not meet the requirements of some public-health orders.[46][47] If respirators with filtered exhalation valves are not available, those with unfiltered exhalation valves may be altered to filter exhalation air, e.g., by using an anesthesia circuit filter.[48] Or the wearer may simply cover the exhalation valve with a surgical mask or other suitable source control material.[49] Care must be taken so that the additional filtration does not impede exhalation to the point that breathing becomes restricted or that excessive CO2 buildup occurs.

CBRN defense

Elastomeric respirators may be used for protection from chemical, biological, radiological, and nuclear agents (CBRN). Some elastomeric respirators are specifically certified for such use.[50]

Gas masks were initially widely used in chemical warfare, against the effects of war gas. Chemical and biological weapons are prohibited by customary international humanitarian law, in international and non-international conflicts. Use is considered a war crime.[51][52][53]

During demonstrations and protests where tear gas (such as CS gas[54]) is employed by riot police, gas masks are commonly used by police[55] and demonstrators alike.[56][57][58] Journalists covering these events also use respirators, and where use of tear gas spreads into residential areas, even those not on the front lines may buy them. Access to respirators has been restricted by authorities who regard them as tools of resistance, causing circumvention and smuggling.[56]

Cleaning and storage

Cleaning a gas mask in the US Navy

Cleaning procedures are specific to the type and material of mask, and are supplied by the manufacturer. They generally involve washing with soap and water or other chemical disinfectants.[2] Some manufacturer instructions have been shown to be much more difficult to understand than reformulated instructions; the lack of standardization also makes cleaning more complicated. Cleaning may be fairly time-consuming, depending on automation and the manufacturer's instructions.[6]

Depending on materials, elastomeric components of masks may be damaged by some cleaning methods (such as acetone, ethanol, strong hypochlorite and iodine solutions, quaternary ammonium salts, ethylene oxide, or temperatures over 50 °C/122 °F). Cleaning by machine is possible, but cleaning can also be done by hand.[2][6] The filter material may be damaged and lose effectiveness if it comes into contact with cleaning or disinfecting solutions. Manufacturers generally advise throwing it out each time the mask is cleaned, but this may not be possible in shortage situations.[2]

Drying a mask may take hours, depending on design (elastomeric straps are typically dry within half-an-hour, but cloth straps take longer). Masks should never be stored wet. The facepiece and straps should not be stored in a way that will distort them.[2] Well-maintained elastomeric masks can last for years in industrial use.[6] Users may carry their respirator in a shoulderbag for accessibility.[6][30]

In construction, elastomeric masks are rarer than disposable mechanical filters; the disposable masks are preferentially issued because supervisors prefer to avoid cleaning and storage.[6]: Box2-1  In industry, when there are few workers, each may be responsible for their own permanently-assigned mask; where there are more workers, there may be a dedicated staff who maintain and reprocess respirators.[6]

Elastomeric respirators may be used by graffiti taggers using aerosol paint canisters.[59]

They are also used by urban explorers venturing into environments where materials such as radioactive particles[60] or asbestos[61] may be present.

Aside from serving their functional purposes, gas masks are also used as fashion in cybergoth wear.[62] They are also used as emblems by some musicians.[63]

See also

Further reading

  • National Academies of Sciences, Engineering; Division, Health and Medicine; Policy, Board on Health Sciences; Care, Committee on the Use of Elastomeric Respirators in Health; Liverman, Catharyn T.; Yost, Olivia C.; Rogers, Bonnie M. E.; Clever, Linda Hawes (2018-12-06). Elastomeric Respirators. National Academies Press (US). {{cite book}}: |last3= has generic name (help)
  • Salas, Mariano Zafra, Javier (2020-10-28). "A room, a bar and a classroom: how the coronavirus is spread through the air". EL PAÍS. Retrieved 2021-04-20.
  • Conocimiento, Ventana al (2021-02-11). "What Have We Learned About Face Masks?". OpenMind. Retrieved 2021-04-20.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 "Elastomeric Respirators: Strategies During Conventional and Surge Demand Situations". U.S. Centers for Disease Control and Prevention. 11 February 2020.
  2. 1 2 3 4 Bach, Michael. "Understanding respiratory protection options in Healthcare: The Overlooked Elastomeric". NIOSH Science Blog. CDC.
  3. 1 2 3 "Respirator Trusted-Source Information: What are they?". U.S. National Institute for Occupational Safety and Health. 2018-01-29. Retrieved 2020-03-27.
  4. ↑ Elastomeric Respirators. National Academies of Science, Engineering, and Medicine. 2018-12-06.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Sciences Policy; Committee on the Use of Elastomeric Respirators in Health Care (2018). "Elastomeric Respirators". In Liverman, Catharyn T.; Yost, Olivia C.; Rogers, Bonnie M. E.; Hawes Clever, Linda (eds.). Reusable Elastomeric Respirators in Health Care: Considerations for Routine and Surge Use. National Academies Press (US). (free fulltext)
  6. 1 2 Alan (22 June 2020). "Open-Source N95 Respirator Mask in the Works". Science and Enterprise.
  7. 1 2 "Understanding Respiratory Protection Against SARS". www.cdc.gov. NPPT, NIOSH, CDC. 5 June 2020. (reviewed April 9th)
  8. ↑ Canadian Centre for Occupational Health and Safety (16 August 2020). "Respirators - Respirator Selection : OSH Answers". www.ccohs.ca. Government of Canada.
  9. 1 2 Godoy, Laura R. Garcia; Jones, Amy E.; Anderson, Taylor N.; Fisher, Cameron L.; Seeley, Kylie M. L.; Beeson, Erynn A.; Zane, Hannah K.; Peterson, Jaime W.; Sullivan, Peter D. (1 May 2020). "Facial protection for healthcare workers during pandemics: a scoping review". BMJ Global Health. 5 (5): e002553. doi:10.1136/bmjgh-2020-002553. ISSN 2059-7908. PMC 7228486. PMID 32371574.
  10. ↑ see image above
  11. ↑ "8000 Series Respirators Particulate Filters, NIOSH Certified". Moldex.
  12. ↑ "Low-Profile Disk Filter, P100, PK2". Grainger Supply.
  13. ↑ Hines, Stella E (April 15, 2020). "Elastomeric Respirators in Healthcare: Lessons learned and adaptation for COVID-19". US National Institutes of Health. Retrieved 7 September 2020.
  14. ↑ Chow, Vivienne. "From protests to coronavirus, a mask revolution has been taking place in Hong Kong". Quartz. Retrieved 10 September 2020., mask type shown here
  15. ↑ Morrison, Robert W. (30 November 2002). "Overview of Current Collective Protection Filtration Technology". Homeland Security Digital Library. U.S. Army Soldier and Biological Chemical Command.
  16. 1 2 "Reuse of Organic Vapor Chemical Cartridges" (PDF). Technical Data Bulletin. 3M. October 2012. #142.
  17. 1 2 3 "NIOSH eliminates maximum use concentrations (MUC) labeling requirement for Chemical Cartridges. | Occupational Safety and Health Administration". www.osha.gov. 3 March 1999. 1910.134(d)(1)(ii).
  18. ↑ NPPTL, NIOSH, CDC (5 June 2020). "Respirator Fact Sheet, What You Should Know". www.cdc.gov.{{cite web}}: CS1 maint: multiple names: authors list (link)
  19. ↑ E. Balieu (1983). "Respirator filters in protection against low-boiling compounds". Journal of the International Society for Respiratory Protection. 1 (1): 125–138. ISSN 0892-6298. Retrieved 20 June 2020.
  20. 1 2 "Cartridge Change Frequently Asked Questions (FAQs)" (PDF). #M.
  21. 1 2 "Respiratory Protection eTool - Respirator Change Schedules". www.osha.gov. [US] Occupational Safety and Health Administration. Retrieved 2019-12-08.
  22. 1 2 3 [US] Occupational Safety and Health Administration. "Respiratory Protection". www.osha.gov. 63:1152-1300.
  23. ↑ Favas, George (July 2005). End of Service Life Indicator (ESLI) for Respirator Cartridges. Part I: Literature Review. Victoria 3207 Australia: Human Protection & Performance Division, Defence Science and Technology Organisation. p. 49.{{cite book}}: CS1 maint: location (link)
  24. 1 2 3 4 5 6 7 8 9 10 Bollinger, Nancy (2004-10-01). "NIOSH respirator selection logic". U.S. National Institute for Occupational Safety and Health: 5–16. doi:10.26616/NIOSHPUB2005100. Retrieved 2020-04-20. For download on Wikimedia Commons: PDF fulltext
  25. ↑ Japan Safety Appliances Association & Japan Standards Association (2006). JIS T 8150 : 2006. Guidance for selection, use and maintenance of respiratory protective devices = 呼吸用保護具の選択，使用及び保守管理方法 (in Japanese). Tokyo: Japan Standards Association. p. 22.
  26. ↑ The Canadian Standards Association (CSA) (2012). CAN/CSA-Z94.4-11. Selection, use, and care of respirators. Ottawa (Ontario). p. 111. ISBN 978-1-55491-684-9.
  27. ↑ БИС/ТК 50 "Лични предпазни средства". Средства за защита на дихателните органи. Препоръки за избор, употреба, грижи и поддържане (in Bulgarian). София: Български институт за стандартизация. p. 54.
  28. ↑ Joint Technical Committee SF-010, Occupational Respiratory Protection (2009). AS/NZS 1715:2009 "Selection, use and maintenance of respiratory protective equipment". Sidney (New South Wales) - Wellington (NZ). p. 105. ISBN 978-0-7337-9000-3.
  29. 1 2 3 Radonovich, Lew (September 5, 2017). "Elastomeric and Powered-Air Purifying Respirators in U.S. Healthcare" (PDF).
  30. 1 2 File:Respirator Types.webm, time 8:19 (loose) and 8:43 (tight-fitting)
  31. 1 2 Brooks, Robyn. "Respiratory Safety: An Interview with Industry Experts -". Occupational Health & Safety Magazine.
  32. ↑ File:Sm90 zerlegt.png
  33. ↑ Popova, Anna, ed. (2018). "Substance #2138 Carbon dioxide". Hygienic standard 2.2.5.3532-18.Occupational exposure limits for toxic substances in workplace air [ГН 2.2.5.3532-18 Предельно допустимые концентрации (ПДК) вредных веществ в воздухе рабочей зоны] (in Russian). Moscow: Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing. p. 170.
  34. ↑ David Caretti; Karen M. Coyne (2008). "Unmanned Assessment of Respirator Carbon Dioxide Levels: Comparison of Methods of Measurement". Journal of Occupational and Environmental Hygiene. 5 (5): 305–312. doi:10.1080/15459620801969998. ISSN 1545-9624. PMID 18330800. S2CID 25173016. Retrieved 20 August 2020.
  35. 1 2 "Welding fumes". Centers for Disease Control and Prevention. NIOSH. 28 March 2018.
  36. ↑ Canadian Centre for Occupational Health and Safety (16 August 2020). "Welding - Fumes And Gases : OSH Answers". www.ccohs.ca. Government of Canada. Retrieved 16 August 2020.
  37. ↑ Jawaid, Asra. "Dealing With Welding Fumes : Resources : American Welding Society". www.aws.org.
  38. ↑ Hallock, Michael. "Tips for Dealing with Respiratory Hazards in Welding -". Occupational Health & Safety.
  39. ↑ National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Board on Health Sciences Policy; Committee on the Use of Elastomeric Respirators in Health Care (2018). "1, Introduction". In Liverman, Catharyn T.; Yost, Olivia C.; Rogers, Bonnie M. E.; Hawes Clever, Linda (eds.). Reusable Elastomeric Respirators in Health Care: Considerations for Routine and Surge Use. National Academies Press (US). (free fulltext)
  40. ↑ "Oil Spill Response Resources - Interim Guidance for Protecting Deepwater Horizon Response Workers and Volunteers". www.cdc.gov. CDC, NIOSH. 11 October 2018.
  41. ↑ "Respiratory Protection on the Farm and Ranch – Ag Safety and Health". ag-safety.extension.org.
  42. ↑ "mplementing Filtering Facepiece Respirator (FFR) Reuse, Including Reuse after Decontamination, When There Are Known Shortages of N95 Respirators". Centers for Disease Control and Prevention. 11 February 2020.
  43. ↑ "Recommended Guidance for Extended Use and Limited Reuse of N95 Filtering Facepiece Respirators in Healthcare Settings". cdc.gov. NIOSH Workplace Safety and Health Topic. CDC. 27 March 2020.
  44. ↑ Respirator cost 30-35 dollars ($19-33 for another mask), ~20 disposable masks/day at $17 per 20. $5–$6.50 per P100 cartridge.[6]
  45. ↑ Wilson, Mark (28 April 2020). "What is a mask valve, and why are cities banning them?". www.msn.com.
  46. ↑ Webeck, Evan (22 April 2020). "Coronavirus: Bay Area mask order takes effect Wednesday. Here's what you need to know". The Mercury News.
  47. ↑ Liu, DCY; Koo, TH; Wong, JKK; Wong, YH; Fung, KSC; Chan, Y; Lim, HS (August 2020). "Adapting re-usable elastomeric respirators to utilise anaesthesia circuit filters using a 3D-printed adaptor - a potential alternative to address N95 shortages during the COVID-19 pandemic". Anaesthesia. 75 (8): 1022–1027. doi:10.1111/anae.15108. PMC 7267584. PMID 32348561.
  48. ↑ Chang, James C. (December 1, 2020). "Demystifying theoretical concerns involving respirators with exhalation valves during COVID-19 pandemic". ajicjournal.org. American Journal of Infection Control.
  49. ↑ Janssen L, Johnson AT, Johnson JS, Mansdorf SZ, Medici OR, Metzler RW, Rehak TR, Szalajda JV. Pittsburgh, PA (29 August 2019). "Chemical, Biological, Radiological, and Nuclear (CBRN) Respiratory Protection Handbook" (PDF). U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH): 229. doi:10.26616/NIOSHPUB2018166. Publication No. 2018-166. Retrieved 12 August 2020. {{cite journal}}: Cite journal requires |journal= (help)CS1 maint: uses authors parameter (link)
  50. ↑ Rule 74. The use of chemical weapons is prohibited., Customary IHL Database, International Committee of the Red Cross (ICRC)/Cambridge University Press.
  51. ↑ Rule 73. The use of biological weapons is prohibited. Archived 12 April 2017 at the Wayback Machine, Customary IHL Database, International Committee of the Red Cross (ICRC)/Cambridge University Press.
  52. ↑ Alexander Schwarz, "War Crimes" in The Law of Armed Conflict and the Use of Force: The Max Planck Encyclopedia of Public International Law Archived 12 April 2017 at the Wayback Machine (eds. Frauke Lachenmann & Rüdiger Wolfrum: Oxford University Press, 2017), p. 1317.
  53. ↑ Lang, Marissa J. (July 26, 2020). "Leaf-blower wars: How Portland protesters are fighting back against tear gas and forming 'walls' of veterans, lawyers, nurses". Washington Post.
  54. ↑ Schumaker, Erin (June 6, 2020). "Why 'tough guy' policing fails". ABC News.
  55. 1 2 Quackenbush, Casey (August 15, 2019). "A run on gas masks: Hong Kong protesters circumvent crackdown on protective gear". Washington Post.
  56. ↑ Tariq, Nia (August 10, 2020). "Corvallis woman donates respirators, tear gas wipes to Portland protesters through GoFundMe campaign". Albany Democrat Herald.
  57. ↑ Kassem, Mustafa (August 8, 2020). "Tear gas, clashes in Beirut amid fury over massive blast". NBC News. Associated Press.
  58. ↑ Abdelkader, Rima (May 14, 2020). "Graffiti artists are using NYC as their canvas". NBC News.
  59. ↑ Loong, Keow Wee (15 July 2016). "Urban explorers in Fukushima's ghost towns – in pictures". The Guardian.
  60. ↑ Watkins, Steve (26 May 2010). "Urban Explorers: New Thrills in Old Buildings". Fort Worth Weekly.
  61. ↑ Valerie Steele, Gothic: Dark Glamour, Yale University Press, 2008, pp. 49–50
  62. ↑ Renshaw, David (1 May 2020). "Car Seat Headrest: from indie recluse to gas mask-wearing party starter?". The Guardian.
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