Mechanical filter (respirator)

Mechanical filter (respirator)
Face mask (filtering facepiece respirator) FFP3 with exhalation valve
Regulation42 CFR 84, EN 149, EN 143
NIOSH scheduleTC-84A
Filtering half mask, reusable elastomeric respirator with pink replaceable pancake filters and grey exhalation valve
Full-face elastomeric respirators seal better.[1]

Mechanical filters, a part of particulate respirators, are a class of filter for air-purifying respirators that mechanically stops particulates from reaching the wearer's nose and mouth. They come in multiple physical forms.

Mechanism of operation

[edit]
Small particles zigzag due to Brownian motion, and are easily captured (diffusion). Large particles get strained out (interception), or have too much inertia to turn, and hit a fiber (impaction). Mid-size particles follow flowlines and are more likely to get through the filter; the hardest size to filter is 0.3 microns diameter.[2]
Filter mechanisms

Mechanical filter respirators retain particulate matter such as dust created during woodworking or metal processing, when contaminated air is passed through the filter material. Wool is still used today as a filter, along with plastic, glass, cellulose, and combinations of two or more of these materials. Since the filters cannot be cleaned and reused and have a limited lifespan, cost and disposability are key factors. Single-use, disposable and replaceable-cartridge models exist.[3]

Mechanical filters remove contaminants from air in the following ways:[4][5]

  1. by interception when particles following a line of flow in the airstream come within one radius of a fiber and adhere to it;[3]
  2. by impaction, when larger particles unable to follow the curving contours of the airstream are forced to embed in one of the fibers directly; this increases with diminishing fiber separation and higher air flow velocity[3]
  3. by an enhancing mechanism called diffusion, where gas molecules collide with the smallest particles, especially those below 100 nm in diameter, which are thereby impeded and delayed in their path through the filter; this effect is similar to Brownian motion and increases the probability that particles will be stopped by either of the two mechanisms above; it becomes dominant at lower air flow velocities[3]
  4. by using electret filter material (usually, electrospun plastic fibers) to attract or repel particles with an electrostatic charge, so that they are more likely to collide with the filter surface[4][5]

More obscure mechanisms include:

  1. by using certain coatings on the fibers that kill or deactivate infectious particles colliding with them (such as salt)[6]
  2. by using gravity and allowing particles to settle into the filter material (this effect is typically negligible)[7]

Considering only particulates carried on an air stream and a fiber mesh filter, diffusion predominates below the 0.1 μm diameter particle size. Impaction and interception predominate above 0.4 μm. In between, near the most penetrating particle size of 0.3 μm, diffusion and interception predominate.[3]

Cross-section of NIOSH-approved P95 filters used in metalworking operations. Even "clean" industrial processes often generate large amounts of harmful particulate matter and require breathing protection.

Materials

[edit]

Mechanical filters can be made of a fine mesh of synthetic polymer fibers.[8][9] The fibers are produced by melt blowing.[10] The fibers are charged as they are blown to produce an electret,[11] and then layered to form a nonwoven polypropylene fabric.[8][9]

Uses

[edit]

Filtering facepiece respirators

[edit]

Filtering facepiece respirators consist mainly of the mechanical filtration medium itself, and are discarded when they become unusable due to damage, dirt, or excessive breathing resistance.[12] Filtering facepieces are typically simple, light, single-piece, half-face masks and employ the first three mechanical filter mechanisms in the list above to remove particulates from the air stream. The most common of these is the white, disposable standard N95 variety; another type is the Surgical N95 mask. It is discarded after single use or some extended period depending on the contaminant. NIOSH recommends not reusing filtering facepieces in biosafety level 2 or 3 laboratories.[13]

Elastomeric respirators

[edit]
A half-face elastomeric air-purifying respirator. This kind of respirator is reusable, with the filters being replaced periodically.
This section is an excerpt from Elastomeric respirator.[edit]

Elastomeric respirators, also called reusable air-purifying respirators,[14] seal to the face with 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.[15]

Elastomeric respirators consist of a reusable mask that seals to the face, with exchangeable filters.[16][17] Elastomeric respirators can be used with chemical cartridge filters that remove gases, mechanical filters that retain particulate matter, or both.[18] As particulate filters, they are comparable[16] (or, due to the quality and error-tolerance of the elastomeric seal, possibly superior[18]) to filtering facepiece respirators such as most disposable N95 respirators and FFP masks.[16]

Powered air-purifying respirators (PAPRs)

[edit]
This section is an excerpt from Powered air-purifying respirator.[edit]
A powered air-purifying respirator (PAPR) is a type of respirator used to safeguard workers against contaminated air. PAPRs consist of a headgear-and-fan assembly that takes ambient air contaminated with one or more type of pollutant or pathogen, actively removes (filters) a sufficient proportion of these hazards, and then delivers the clean air to the user's face or mouth and nose. They have a higher assigned protection factor than filtering facepiece respirators such as N95 masks. PAPRs are sometimes called positive-pressure masks, blower units, or just blowers.

Filtration standards

[edit]

U.S. standards (N95 and others)

[edit]
A video describing N95 certification testing
This section is an excerpt from NIOSH air filtration rating § 42 CFR 84.[edit]

Under the current revision of Part 84 established in 1995, NIOSH established nine classifications of approved particulate filtering respirators based on a combination of the respirator series and efficiency level. The first part of the filter's classification indicates the series using the letters N, R, or P to indicate the filter's resistance to filtration efficiency degradation when exposed to oil-based or oil-like aerosols (e.g., lubricants, cutting fluids, glycerine, etc.).[19][20][21] Definitions and intended use for each series is indicated below.[22]

  • N for not resistant to oil. Used when oil particulates are not present. Tested using sodium chloride particles.
  • R for resistant to oil. Used when oil particulates are present and the filter is disposed of after one shift. Tested using dioctyl phthalate (DOP) oil particles.
  • P for oil-proof. Used when oil particulates are present and the filter is re-used for more than one shift. Tested with DOP oil particles.

The second value indicates the minimum efficiency level of the filter. When tested according to the protocol established by NIOSH each filter classification must demonstrate the minimum efficiency level indicated below.

NIOSH particulate respirator class minimum efficiency levels[19]
Particulate Respirator class Minimum efficiency
level 		Permitted for TB
NaCl (N) or DOP (R,P) N95, R95, P95 95% Yes
N99, R99, P99 99%
N100, R100, P100 99.97%

All respirator types are permitted for TB.[23][24] Class-100 filters can block asbestos.[25] For N type filters, a 200 mg load of NaCl is used, with and undefined service time. For R type filters, a 200 mg of DOP is used, with a defined service time of "one work shift". For P type filters, an indefinite amount of DOP is used until filtration efficiency stabilizes.[26] P100 filters, under 42 CFR part 84, are the only filters permitted to be magenta in color.[27]

HE (high-efficiency) labeled filters (described in the subsection) are only provided for powered air-purifying respirators. HE-marked filters are 99.97% efficient against 0.3 micron particles and are oil-proof.[28][29][30]

Since filters are tested against the by definition most penetrating particle size of 0.3 μm, an APR with a P100 classification would be at least 99.97% efficient at removing particles of this size.[21] Particles with a size both less than and greater than 0.3 μm may be filtered at an efficiency greater than 99.97%.[31][32] However, this may not always be the case, as the most penetrating particle size for N95s was measured to be below 0.1 μm, as opposed to the predicted size of between 0.1 and 0.3 μm.[33]

European standards (FFP2 and others)

[edit]
FFP2 masks
Face mask FFP2 without exhalation valve
This section is an excerpt from European respirator standards § EN 149.[edit]

The EN 149 standard defines performance requirements for three classes of particle-filtering half masks: FFP1, FFP2 and FFP3. The protection provided by an FFP2 (or FFP3) mask includes the protection provided by a mask of the lower-numbered classes.

A mask conforming to the standard must have its class written on it, along with the name of the standard and its year of publication, as well as any applicable option codes, e.g. “EN 149:2001 FFP1 NR D”. Some manufacturers use in addition the colour of the elastic band to identify the mask class, however, the EN 149 standard does not specify any such colour coding and different manufacturers have used different colour schemes.

Class[34] Filter penetration limit (at 95 L/min air flow) Inward leakage Typical elastic band
FFP1 Filters at least 80% of airborne particles <22% Yellow
FFP2 Filters at least 94% of airborne particles <8% Blue or White
FFP3 Filters at least 99% of airborne particles <2% Red
3M 2091 filter with P3-BR approval

European standard EN 143 defines the 'P' classes of particle filters that can be attached to a face mask. These filters are typically used on reusable respirators, like elastomeric respirators.[35]

Standard Class Filter type Filter penetration limit (at 95 L/min air flow) Inward leakage Typical elastic band
EN 14683[36] Type I Mask Less than 98% droplet filtration, intended for use by patients N/A N/A
Type II Not fluid-resistant, 98% droplet filtration, intended for use by healthcare workers in droplet-free environments
Type IIR Fluid-resistant, 98% droplet filtration, surgical
EN 143 P1 Attachment Filters at least 80% of airborne particles N/A N/A
P2 Filters at least 94% of airborne particles
P3 Filters at least 99.95% of airborne particles
Both European standard EN 143 and EN 149 test filter penetration with dry sodium chloride and paraffin oil aerosols after storing the filters at 70 °C (158 °F) and −30 °C (−22 °F) for 24 h each. The standards include testing mechanical strength, breathing resistance and clogging. EN 149 tests the inward leakage between the mask and face, where 10 human subjects perform 5 exercises each. The truncated mean of average leakage from 8 individuals must not exceed the aforementioned values.[37]: § 8.5 

Other standards (KN95 and others)

[edit]
"KN95" redirects here. For the US standard, see N95 respirator.
Chinese standard for respirators
Face mask KN95

Respirator standards around the world loosely fall into the two camps of US- and EU-like grades. According to 3M, respirators made according to the following standards are equivalent to US N95 or European FFP2 respirators "for filtering non-oil-based particles such as those resulting from wildfires, PM 2.5 air pollution, volcanic eruptions, or bioaerosols (e.g. viruses)":[38]

  • Chinese KN95 (GB2626-2006): similar to US. Has category KN (non-oily particles) and KP (oily particles), 90/95/100 versions. EU-style leakage requirements.[39][40] In China, KN95 respirators are made by companies such as Guangzhou Harley,[41] Guangzhou Powecom,[42] Shanghai Dasheng[43] and FLTR.[44]
  • Korean 1st Class (KMOEL - 2017–64), also referred to as "KF94": EU grades, KF 80/94/99 for second/first/special.[45] In Korea, KF94 respirators are made by companies such as LG, Soomlab,[46] Airqueen,[47] Kleannara,[48] Dr. Puri,[49] Bluna[50] and BOTN.[51]

The NPPTL has also published a guideline for using non-NIOSH masks instead of the N95 in the COVID-19 response. The OSHA has a similar document. The following respirator standards are considered similar to N95 in the US:[52][53]

  • Japanese DS2/RS2 (JMHLW-Notification 214, 2018): EU-like grades with two-letter prefix – first letter D/R stands for disposable or replaceable; second letter S/L stands for dry (NaCl) or oily (DOP oil) particles.[7] Japanese DS2 respirators are made by companies such as Hogy Medical,[54] Koken,[55] Shigematsu,[56] Toyo Safety,[57] Trusco,[58] Vilene[59] and Yamamoto Safety.[60]
  • Mexican N95 (and others) (NOM-116-2009): same grades as in NIOSH.[61]
  • Brazilian PFF2 (ABNT/NBR 13698:2011): EU-like grades.[62]

Disinfection and reuse

[edit]

Hard filtering facepiece respirator masks are generally designed to be disposable, for 8 hours of continuous or intermittent use. One laboratory found that there was a decrease in fit quality after five consecutive donnings.[63] Once they are physically too clogged to breathe through, they must be replaced.

Hard filtering facepiece respirator masks are sometimes reused, especially during pandemics, when there are shortages. Infectious particles could survive on the masks for up to 24 hours after the end of use, according to studies using models of SARS-CoV-2;[63] In the COVID-19 pandemic, the US CDC recommended that if masks run short, each health care worker should be issued with five masks, one to be used per day, such that each mask spends at least five days stored in a paper bag between each use. If there are not enough masks to do this, they recommend sterilizing the masks between uses.[64] Some hospitals have been stockpiling used masks as a precaution.[65] The US CDC issued guidelines on stretching N95 supplies, recommending extended use over re-use. They highlighted the risk of infection from touching the contaminated outer surface of the mask, which even professionals frequently unintentionally do, and recommended washing hands every time before touching the mask. To reduce mask surface contamination, they recommended face shields, and asking patients to wear masks too ("source masking").[66]

Apart from time, other methods of disinfection have been tested. Physical damage to the masks has been observed when microwaving them, microwaving them in a steam bag, letting them sit in moist heat, and hitting them with excessively high doses of ultraviolet germicidal irradiation (UVGI). Chlorine-based methods, such as chlorine bleach, may cause residual smell, offgassing of chlorine when the mask becomes moist, and in one study, physical breakdown of the nosepads, causing increased leakage.[63] Fit and comfort do not seem to be harmed by UVGI, moist heat incubation, and microwave-generated steam.[63]

Some methods may not visibly damage the mask, but they ruin the mask's ability to filter. This has been seen in attempts to sterilize by soaking in soap and water, heating dry to 160 °C (320 °F), and treating with 70% isopropyl alcohol, and hydrogen peroxide gas plasma[63] (made under a vacuum with radio waves[67]). The static electrical charge on the microfibers is destroyed by some cleaning methods. UVGI (ultraviolet light), boiling water vapour, and dry oven heating do not seem to reduce the filter efficiency, and these methods successfully decontaminate masks.[63]

UVGI (an ultraviolet method), ethylene oxide, dry oven heating and vaporized hydrogen peroxide are currently the most-favoured methods in use in hospitals, but none have been properly tested.[63] Where enough masks are available, cycling them and reusing a mask only after letting it sit unused for five days is preferred.[64]

It has been shown that masks can also be sterilized by ionizing radiation.[68] Gamma radiation and high energy electrons penetrate deeply into the material and can be used to sterilize large batches of masks within a short time period. The masks can be sterilized up to two times but have to be recharged after every sterilization as the surface charge is lost upon radiation.

A recent development is a composite fabric that can deactivate both biological and chemical threats.[69]

References

[edit]
  1. ^ "Elastomeric Respirators: Strategies During Conventional and Surge Demand Situations". U.S. Centers for Disease Control and Prevention. 11 February 2020.
  2. ^ Wei, Neo Kang (6 May 2019). "What is PM0.3 and Why Is It Important?". Smart Air Filters.
  3. ^ a b c d e TSI Incorporated. "Mechanisms of Filtration for High Efficiency Fibrous Filters - Application Note ITI-041" (PDF). Retrieved 29 April 2020.
  4. ^ a b perry, J.L.; Agui, J.H.; Vijayakumar, R. (May 2016), Submicron and Nanoparticulate Matter Removal by HEPA-Rated Media Filters and Packed Beds of Granular Materials (PDF), NASA
  5. ^ a b "Guidance for Filtration and Air-Cleaning Systems to Protect Building Environments from Airborne Chemical, Biological, or Radiological Attacks" (PDF). CDC NIOSH. April 2003. doi:10.26616/NIOSHPUB2003136.
  6. ^ Quan, Fu-Shi; Rubino, Ilaria; Lee, Su-Hwa; Koch, Brendan; Choi, Hyo-Jick (2017-01-04). "Universal and reusable virus deactivation system for respiratory protection". Scientific Reports. 7 (1): 39956. Bibcode:2017NatSR...739956Q. doi:10.1038/srep39956. ISSN 2045-2322. PMC 5209731. PMID 28051158.
  7. ^ a b "Standard for Dust Mask". JICOSH Home.
  8. ^ a b Xie, John (2020-03-19). "World Depends on China for Face Masks But Can Country Deliver?". Voice of America.
  9. ^ a b Evan, Melanie; Hufford, Austen (March 7, 2020). "Critical Component of Protective Masks in Short Supply - The epidemic has driven up demand for material in N95 filters; 'everyone thinks there is this magic factory somewhere'". The Wall Street Journal.
  10. ^ Feng, Emily (2020-03-16). "COVID-19 Has Caused A Shortage Of Face Masks. But They're Surprisingly Hard To Make". NPR.
  11. ^ US 4215682A 
  12. ^ "Respirator Trusted-Source Information: What are they?". U.S. National Institute for Occupational Safety and Health. 2018-01-29. Archived from the original on 2020-03-28. Retrieved 2020-03-27.
  13. ^ "Filtering out Confusion: Frequently Asked Questions about Respiratory Protection" (PDF). NIOSH. 2018. doi:10.26616/NIOSHPUB2018128. Archived (PDF) from the original on 9 April 2023. Retrieved 29 May 2024.
  14. ^ "Elastomeric Respirators: Strategies During Conventional and Surge Demand Situations". U.S. Centers for Disease Control and Prevention. 11 February 2020. Archived from the original on 2023-02-11.
  15. ^ a b c Bach, Michael (6 July 2017). "Understanding respiratory protection options in Healthcare: The Overlooked Elastomeric". NIOSH Science Blog. CDC.
  16. ^ "Respirator Trusted-Source Information: What are they?". U.S. National Institute for Occupational Safety and Health. 2018-01-29. Retrieved 2020-03-27.
  17. ^ a b Liverman CT, Yost OC, Rogers BM, et al., eds. (2018-12-06). "Elastomeric Respirators". Reusable Elastomeric Respirators in Health Care: Considerations for Routine and Surge Use. National Academies Press.
  18. ^ a b "42 CFR Part 84 - Approval of Respiratory Protective Devices". ecfr.gov. United States Government Publishing Office. February 6, 2020. Archived from the original on 23 February 2020. Retrieved February 9, 2020.
  19. ^ "Respirator Trusted-Source Information Section 1: NIOSH-Approved Respirators". The National Personal Protective Technology Laboratory (NPPTL). Centers for Disease Control and Prevention. January 29, 2018. Archived from the original on 16 June 2019. Retrieved February 9, 2020.
  20. ^ a b "NIOSH Guide to the Selection and Use of Particulate Respirators". The National Institute for Occupational Safety and Health (NIOSH). Centers for Disease Control and Prevention. June 6, 2014 [January 1996]. Archived from the original on 11 August 2019. Retrieved February 9, 2020.
  21. ^ "OSHA Technical Manual Section 8VII: Chapter 2 Respiratory Protection Appendix 2-4". OSHA (TED 01-00-015 ed.). Archived from the original on 28 September 2019. Retrieved February 9, 2020.
  22. ^ "TB Respiratory Protection Program In Health Care Facilities Administrator's Guide" (PDF). U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. September 1999. doi:10.26616/NIOSHPUB99143. Archived (PDF) from the original on 10 October 2022. Retrieved 14 June 2024.
  23. ^ "DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service 42 CFR Part 84" (PDF). US Federal Register. pp. 26850-26893. Archived (PDF) from the original on 8 May 2024. Retrieved 2024-05-08.
  24. ^ "NIOSH Pocket Guide - Asbestos". CDC. Archived from the original on 20 June 2024. Retrieved 20 June 2024.
  25. ^ "DHHS Pub 96-101 NIOSH Guide to the Selection & Use of Particulate Respirators Certified Under 42 CFR 84". NIOSH.
  26. ^ Herring Jr., Ronald N. (1997). "42 CFR Part 84: It's time to change respirators... but how?". Engineer's Digest. pp. 14–23.
  27. ^ "Considerations for Optimizing the Supply of Powered Air-Purifying Respirators (PAPRs)". U.S. Centers for Disease Control and Prevention. 2020-04-19. Archived from the original on 6 January 2023. Retrieved 2020-05-25.
  28. ^ Vanessa, Roberts (Fall 2014). "To PAPR or Not to PAPR?". Canadian Journal of Respiratory Therapy. 50 (3): 87–90. PMC 4456839. PMID 26078617.
  29. ^ "Understanding Respiratory Protection Against SARS". U.S. National Institute for Occupational Safety and Health. 2020-04-09. Archived from the original on 6 December 2020. Retrieved 2020-05-26.
  30. ^ "NIOSH Guide to the Selection and Use of Particulate Respirators Appendix E: Commonly Asked Questions and Answers About Part 84 Respirators". The National Institute for Occupational Safety and Health (NIOSH). Centers for Disease Control and Prevention. June 6, 2014. Archived from the original on 20 June 2019. Retrieved February 9, 2020.
  31. ^ "CDC - NIOSH Publications and Products - Appendices for 96-101". www.cdc.gov. 2018-10-16. Archived from the original on 20 June 2019. Retrieved 2020-06-22.
  32. ^ Lee, Byung Uk; Yermakov, Mikhail; Grinshpun, Sergey A. (2005). "Filtering Efficiency of N95- and R95-Type Facepiece Respirators, Dust-Mist Facepiece Respirators, and Surgical Masks Operating in Unipolarly Ionized Indoor Air Environments" (PDF). Aerosol and Air Quality Research. 5 (1): 25–38. doi:10.4209/aaqr.2005.06.0003. Archived (PDF) from the original on 20 January 2022. Retrieved 4 July 2024.
  33. ^ "Fiche pratique de sécurité ED 105. Appareils de protection respiratoire et métiers de la santé" (PDF). inrs.fr. INRS. Retrieved 7 April 2020.
  34. ^ "Fiche pratique de sécurité ED 105. Appareils de protection respiratoire et métiers de la santé" (PDF). inrs.fr. INRS. Retrieved 7 April 2020.
  35. ^ "COVID-19 Technical Specifications for Personal Protective Equipment and Related IPC supplies" (PDF). World Health Organization.
  36. ^ "NF EN 149+A1". www.boutique.afnor.org. September 2009. alternative source
  37. ^ "Technical Bulletin: Comparison of FFP2, KN95, and N95 and Other Filtering Facepiece Respirator Classes" (PDF). 3M Personal Safety Division. January 2020.
  38. ^ "China Releases an Updated Mandatory Standard GB 2626-2019 Respiratory Protection - Non-Powered Air-Purifying Particle Respirator". HKTDC Research. 20 April 2020. Classification and Marking: 2. Filter element categorization. Retrieved 27 July 2020.
  39. ^ "China Mandatory Standard GB 2626-2019 Respiratory Protection—Non-Powered Air-Purifying Particle Respirator Effective Date Postponed to July 1 2021" (PDF). Bureau Veritas. 24 June 2020. Retrieved 27 July 2020.
  40. ^ "建站成功". harleykn95.com.
  41. ^ "Powecom - home page". www.powecom.com.
  42. ^ "Dasheng Health Products Manufacturing". www.dashengmask.com.
  43. ^ "FLTR95 Sealing Face Masks 100PK - White".
  44. ^ Jung, Hyejung; Kim, Jongbo; Lee, Seungju; Lee, Jinho; Kim, Jooyoun; Tsai, Perngjy; Yoon, Chungsik (2014). "Comparison of Filtration Efficiency and Pressure Drop in Anti-Yellow Sand Masks, Quarantine Masks, Medical Masks, General Masks, and Handkerchiefs". Aerosol and Air Quality Research. 14 (3): 991–1002. doi:10.4209/aaqr.2013.06.0201.
  45. ^ "[Global] Soomlab Mask".
  46. ^ "HOME". AirQUEEN™ Nano Mask.
  47. ^ "Main products".
  48. ^ "DR. PURI KF94 MASK | DR PURI KF94 FACE MASK MADE IN KOREA". drpurimask.com. Archived from the original on 2020-11-01.
  49. ^ "블루나(BLUNA) 프리미엄 아기물티슈". 블루나(BLUNA) 프리미엄 아기물티슈.
  50. ^ "TIA - BOTN KF94". en.botn.co.kr.
  51. ^ "NPPTL Respirator Assessments to Support the COVID-19 Response, International Respirator Assessment Request". NPPTL | NIOSH | CDC. 24 April 2020.
  52. ^ "Enforcement Guidance for Use of Respiratory Protection Equipment Certified under Standards of Other Countries or Jurisdictions During the Coronavirus Disease 2019 (COVID-19) Pandemic". Occupational Safety and Health Administration.
  53. ^ "株式会社ホギメディカル".
  54. ^ "クリーン、ヘルス、セーフティで社会に 興研株式会社". www.koken-ltd.co.jp.
  55. ^ "使い捨て式防じんマスク | 製品情報 | 株式会社 重松製作所".
  56. ^ "国家検定合格品 - メガネ - 製品情報 - トーヨーセフティー".
  57. ^ "TRUSCO トラスコ中山株式会社". www.trusco.co.jp.
  58. ^ "製品情報: メディカル資材 医療用マスク&キャップ". www.vicre.co.jp.
  59. ^ "使い捨て式マスク,使い捨て式防じんマスク(Ds2) | Yamamoto 公式オンラインショップ | Yamamoto Safety Online Shop".
  60. ^ "NORMA Oficial Mexicana NOM-116-STPS-2009, Seguridad-Equipo de protección personal-Respiradores purificadores de aire de presión negativa contra partículas nocivas-Especificaciones y métodos de prueba". Retrieved 2024-07-16.
  61. ^ "NORMA BRASILEIRA E quip amento de proteção respiratória — Peça semifacial fi ltrante para partículas" (PDF). Retrieved 2024-07-16.
  62. ^ a b c d e f g 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.
  63. ^ a b "Coronavirus Disease 2019 (COVID-19)". Centers for Disease Control and Prevention. 11 February 2020.
  64. ^ Mills, Stu (10 April 2020). "Researchers looking at innovative ways to sterilize single-use masks". Canadian Broadcasting Corporation.
  65. ^ "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.
  66. ^ "Hydrogen Peroxide Gas Plasma". cdc.gov. Disinfection & Sterilization Guidelines, Guidelines Library, Infection Control. 2019-04-04.
  67. ^ Pirker, Luka; Krajnc, Anja Pogačnik; Malec, Jan; Radulović, Vladimir; Gradišek, Anton; Jelen, Andreja; Remškar, Maja; Mekjavić, Igor B.; Kovač, Janez; Mozetič, Miran; Snoj, Luka (2020-10-01). "Sterilization of polypropylene membranes of facepiece respirators by ionizing radiation". Journal of Membrane Science. 619: 118756. doi:10.1016/j.memsci.2020.118756. ISSN 0376-7388. PMC 7528844. PMID 33024349.
  68. ^ Cheung, Yuk Ha; Ma, Kaikai; van Leeuwen, Hans C.; Wasson, Megan C.; Wang, Xingjie; Idrees, Karam B.; Gong, Wei; Cao, Ran; Mahle, John J.; Islamoglu, Timur; Peterson, Gregory W.; de Koning, Martijn C.; Xin, John H.; Farha, Omar K. (October 13, 2021). "Immobilized Regenerable Active Chlorine within a Zirconium-Based MOF Textile Composite to Eliminate Biological and Chemical Threats". Journal of the American Chemical Society. 143 (40): 16777–16785. doi:10.1021/jacs.1c08576. PMID 34590851. S2CID 238229650 – via ACS Publications.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Mechanical_filter_(respirator)&oldid=1252693976#Other_standards_(KN95_and_others)"