Elastomeric respirator

Elastomeric respirators are a type of respirator that seals to the face using elastomers (synthetic rubbers). They are generally reusable. There are two main types: air-purifying (filtering) and air-supplying. Full-face versions of elastomeric respirators seal better and protect the eyes.[1]

Protective P100 half-face elastomeric filter mask worn by a NYPD officer
Elastomeric full-face masks also protect the eyes. Pink pancake-type particulate filters make their presence or absence conspicuous at a distance.

Air-purifying elastomeric respirators (also called reusable air-purifying respirators[2]) 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 masks and FPP masks).[3]

Elastomeric air-purifying respirators are reusable because the facepiece is cleaned and reused, but the filter cartridges 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.[7][1]

Elastomeric air-supplying respirators have similar seals, but they don't filter the ambient air; they provide replacement air. They leak outwards and are thus much better at keeping hazards out. See self-contained breathing apparatus and oxygen mask.

Types

Respirators may be either air-supplying or air-filtering.[8] Air-supplying respirators are 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.[9]

Filter types
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.

The masks and filters come in a variety of standards for mechanical filters and for chemical cartridges, intended for a variety of purposes.[10] An appropriate standard of filter must be used for the mask to be effective.[1]

Filters may be contained in cartridges or canisters; there are also flexible pancake-style filters (see illustrations).[1]

As of 2020, the commercially available particulate filter cartridges are disposable, and must be replaced when damaged (physically or chemically, torn or soiled with something that will damage the filter, such as many fluids), contaminated (the outside has caught dangerous particulates; for instance, infectious particles), or clogged due to accumulated particles, so that breathing resistance is too high.[1]

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. It is dependent on many factors,[6] includign environmental factors like humidity. There is active research into making more types of chemical cartridge with an end-of-service-life indicator, which indicates to the user when the cartridge has expired.[11] Chemical, especially the more volatile chemicals, may desorb from the filter and diffuse through the cartridge while it is not in use, such that they may be breathed by a wearer re-using the cartridge.[11] In principle, many cartridges can be treated to desorb the toxic chemicals, renewing them, but in practice this is not done for respirator filters, only in more predictable fixed installations (details).

Most masks take one or two filters;[6] if there are two, one may be used for inhalation and one for exhalation.

Communication

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 mike, have also been used.[6]

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

Comfort

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. 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]

Efficiency

Fit
This pilot's oxygen mask is an orinasal mask, and an air-supplying mask

Fit is critical to the protection provided by elastomeric respirators. Elastomeric masks must be individually fit-tested and inspected for full efficacy.[1] 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]

Elastomeric respirators include:[8]

  • 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

Full-face elastomeric respirators generally seal better.[1] For substances hazardous to the eyes, a respirator equipped with a full facepiece, helmet, or hood is recommended.[12]

Respirators are rated by assigned protection factor. The APF is the ratio of concentrations outside divided by concentrations inside.[13] Half-mask unpowered air-purifying elastomeric respirators have an AFP of 10, full-face ones have an AFP of 50,[9] for both particulates and gasses.[12]

For contrast, disposable filtering facepiece respirators have an APF of 10 for particulates only.[12] Powered air-purifying elastomeric respirators (PAPRs) have an AFP of 25, full-face elastomeric supplied-air respirators (SARs) have an AFP of 100, and an elastomeric self-contained breathing apparatus (SCBA) has an AFP of 10 000.[9]

Interference with seals
A CDC guide to facial hair and respirators

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.[1][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,[1] 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]

Usage errors

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.[14]

Indications for use

Air-purifying respirators cannot be used in oxygen-deficient atmospheres (less than 19.5% oxygen). Nor can they be used in atmospheres with a hazard level that may be immediately dangerous to life or health. Air-supplying respirators must be used.[12] The respirator must have a sufficient APF for the conditions. If concentrations of hazardous particulates or gasses that are greater than the occupational exposure limit, US NIOSH regulations require that respirators be worn, but they may also be worn at lower concentrations.[12]

Materials

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]

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.[1] 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 an 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.[1][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.[1]

Drying a mask may take hours, depending on design. Masks should never be stored wet. The facepiece and straps should not be stored in a way that will distort them.[1] Well-maintained elastomeric masks can last for years in industrial use.[6] Users may carry their respirator in a shoulderbag for accessibility.[6][13]

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]

Uses

Industrial use
A worker in a plant nursery wears a respirator to protect against the insecticides sprayed in the greenhouses, 1930.

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.[12]

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.[15][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.[16][17] A self-contained breathing apparatus may be needed.[15] Respirators used by welders must fit under a welding mask.[18]

Respirators are also used in demolition to protect against asbestos, mould, and other hazardous waste.[19]

Elastomeric respirators are used for cleaning up after oil spills.[20]

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.[14]

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.[21]

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

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.[13] Elastomeric respirators were used as a substitute for N95 masks among shortages during the 2020 COVID-19 pandemic.[1] 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.[1]

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.[1] 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.[1] 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.[22][23]

Some elastomeric masks have unfiltered exhalation valves; these are not recommended in disease-control settings where the unfiltered exhaled air might infect others (for instance, surgery).[1]

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.[24] Air-supplying respirators may be easier for hospital personnel to use; they can be worn for longer periods.[9]

CBRN defense
A mother and baby, both in gas-masks, during WWII.
Police respond to a terrorist attack in Japan.

Elastomeric respirators may be used for protection from chemical, biological, radiological, and nuclear agents (CBRN). Some elastomeric respirators are specifically certified for such use.[25]

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.[26][27][28]

During demonstrations and protests where tear gas (such as CS gas[29]) is employed by riot police, gas masks are commonly used by police[30] and demonstrators alike.[31][32][33] 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.[31]

A respirator as part of a dancer's cybergoth outfit.
A singer performing in an elastomeric respirator (but without its filter cartridges) in 2002.

Elastomeric respirators may be used by graffiti taggers using aerosol paint canisters.[34]

They are also used by urban explorers venturing into environments where materials such as radioactive particles[35] or asbestos[36] may be present.

Aside from serving their functional purposes, gas masks are also used as fashion in cybergoth wear.[37] They are also used as emblems by some musicians.[38]

See also
  • Respirator for other types of air-filtering respirators
  • Mechanical filter respirator for other types of particulate filters
  • Air-purifying respirators like elastomeric respirators are slightly less protective than air-supplying respirators and SCBAs.[6]

References
  1. "Elastomeric Respirators: Strategies During Conventional and Surge Demand Situations". U.S. Centers for Disease Control and Prevention. 11 February 2020.
  2. "PPE Image Gallery: Respiratory Protective Equipment - Civilian - Radiation Emergency Medical Management". www.remm.nlm.gov.
  3. Bach, Michael. "Understanding respiratory protection options in Healthcare: The Overlooked Elastomeric". NIOSH Science Blog. CDC.
  4. "Respirator Trusted-Source Information: What are they?". U.S. National Institute for Occupational Safety and Health. 2018-01-29. Retrieved 2020-03-27.
  5. Elastomeric Respirators. National Academies of Science, Engineering, and Medicine. 2018-12-06.
  6. 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)
  7. Alan (22 June 2020). "Open-Source N95 Respirator Mask in the Works". Science and Enterprise.
  8. Canadian Centre for Occupational Health and Safety (16 August 2020). "Respirators - Respirator Selection : OSH Answers". www.ccohs.ca. Government of Canada.
  9. "Understanding Respiratory Protection Against SARS". www.cdc.gov. NPPT, NIOSH, CDC. 5 June 2020. (reviewed April 9th)
  10. "Cartridge Change Frequently Asked Questions (FAQs)" (PDF). #M.
  11. Bollinger, Nancy (2004-10-01). "NIOSH respirator selection logic". U.S. National Institute for Occupational Safety and Health. pp. 5–16. doi:10.26616/NIOSHPUB2005100. Retrieved 2020-04-20. For download on Wikimedia Commons: PDF fulltext
  12. Radonovich, Lew (September 5, 2017). "Elastomeric and Powered-Air Purifying Respirators in U.S. Healthcare" (PDF).
  13. Brooks, Robyn. "Respiratory Safety: An Interview with Industry Experts -". Occupational Health & Safety Magazine.
  14. "Welding fumes". Centers for Disease Control and Prevention. NIOSH. 28 March 2018.
  15. 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.
  16. Jawaid, Asra. "Dealing With Welding Fumes : Resources : American Welding Society". www.aws.org.
  17. Hallock, Michael. "Tips for Dealing with Respiratory Hazards in Welding -". Occupational Health & Safety.
  18. 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)
  19. "Oil Spill Response Resources - Interim Guidance for Protecting Deepwater Horizon Response Workers and Volunteers". www.cdc.gov. CDC, NIOSH. 11 October 2018.
  20. "Respiratory Protection on the Farm and Ranch – Ag Safety and Health". ag-safety.extension.org.
  21. "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.
  22. "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.
  23. 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]
  24. 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 requires |journal= (help)CS1 maint: uses authors parameter (link)
  25. Rule 74. The use of chemical weapons is prohibited., Customary IHL Database, International Committee of the Red Cross (ICRC)/Cambridge University Press.
  26. 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.
  27. 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.
  28. 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.
  29. Schumaker, Erin (June 6, 2020). "Why 'tough guy' policing fails". ABC News.
  30. Quackenbush, Casey (August 15, 2019). "A run on gas masks: Hong Kong protesters circumvent crackdown on protective gear". Washington Post.
  31. Tariq, Nia (August 10, 2020). "Corvallis woman donates respirators, tear gas wipes to Portland protesters through GoFundMe campaign". Albany Democrat Herald.
  32. Kassem, Mustafa (August 8, 2020). "Tear gas, clashes in Beirut amid fury over massive blast". NBC News. Associated Press.
  33. Abdelkader, Rima (May 14, 2020). "Graffiti artists are using NYC as their canvas". NBC News.
  34. Loong, Keow Wee (15 July 2016). "Urban explorers in Fukushima's ghost towns – in pictures". The Guardian.
  35. Watkins, Steve (26 May 2010). "Urban Explorers: New Thrills in Old Buildings". Fort Worth Weekly.
  36. Valerie Steele, Gothic: Dark Glamour, Yale University Press, 2008, p. 49-50
  37. Renshaw, David (1 May 2020). "Car Seat Headrest: from indie recluse to gas mask-wearing party starter?". The Guardian.
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