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The Masks, the Myths, the Controversy

Jul 1, 2020, 21:30 PM by Jennifer Noerenberg, MD

With the COVID-19 pandemic, masks have become increasingly indispensable because the mode of transmission of coronavirus is presumed to be by droplet/contact and the clinical symptoms seem to predominantly impact the respiratory system.  With the speed of transmission and prevalence of the disease, demand for masks as a critical component of PPE has exceeded production. Therefore, it has become more important than ever to understand the differences between masks and the various modalities of reprocessing to safely protect and extend their usage.  

With the speed of transmission and prevalence of the disease, demand for masks as a critical component of PPE has exceeded production.

Recommendations for mask utilization differ between sources and intended audiences.  For the public, the message is driven by a profound need to provide education and ensure proper usage.  One interpretation of the Centers for Disease Control and Prevention (CDC) recommendations for the routine use of masks by members of the public states that “While wearing a mask will prevent you from spreading COVID-19 if you have it and don’t know it, social and physical distancing and frequent, thorough handwashing are still the best ways to avoid getting COVID-19.”[1]

The World Health Organization’s recommendations take a more conservative approach, urging medical masks (a more specific type than referenced by the CDC) to be reserved for medical personnel and those who are symptomatic.  They caution that when wearing a mask, members of the public may be imbued with a false sense of security and other important measures such as physical distancing and hand hygiene may be neglected. In addition, there may be improper donning and inadvertent face touching while adjusting the mask which can increase the risk of self-contamination.[2] 

Types of Masks

Medical providers (especially anesthesiologists) are at elevated risk for contracting COVID-19 due to the frequency of exposure and the routine performance of aerosol-generating medical procedures. It also may be challenging to practice social distancing while caring for patients in an operating room environment.  Anesthesia providers frequently encounter two types of masks.

A surgical mask provides some fluid resistance and protection against large droplets, splashes, or sprays and stops a large portion of droplets and aerosols emitted from the wearer.[3] Surgical masks do not offer a tight fit and do not require fit testing for protection.  The mask should cover both the nose and mouth simultaneously and should, ideally, not be touched or adjusted once applied.  In the medical setting, most of these are single use and disposable; however, with shortages in personal protective equipment (PPE), there have been some attempts to prolong use by storing masks in paper bags or ventilated containers.[3] Although this is a controversial tactic, provided that the mask is not soiled or damp, it can potentially be reused as a solution to rationing usage.  There is no “approved” way to clean or disinfect standard medical masks, as germicidal wipes or sprays and alcohol damage mask integrity and filtering capabilities.

The second type of mask that anesthesiologists frequently see is a tight-fitting mask that reduces the wearer’s exposures to small particles, aerosols, and droplets (eg, N-95 masks).  These masks are designed to filter ambient air and require users to be fitted to ensure a tested seal. Common nomenclature consists of an “N” to indicate the mask does not protect against oily substances and a “P” to indicate the mask is oil proof.  A respiratory droplet or aerosol is water based, so either the “N” or “P” type filter should work.  The associated number is the percentage of size 0.3 micron and larger particles that are filtered.  There are disposable models and reusable models.[4] Many disposable masks have the advantage of being designated as medical grade.[5] Although reusable, elastomeric masks have filters that accomplish the same goal, the manufacturer may not have taken the step to have the mask evaluated for medical applications.  Nonetheless, amid the COVID-19 pandemic, the U.S. Food and Drug Administration (FDA) has approved the use of these masks in clinical settings. Several methods are available to extend the use of disposable filtering facepiece respirators.  With regard to reusable respirators, guidelines for cleaning between uses and at the end of shifts, as well as suggestions for management of the filters, are available.[4] Notably, most reusable models do not have a filtered expiratory valve. The lack of a filtered expiratory valve might be relevant in COVID positive or suspected patients, but evidence suggesting infectious materials exhausting out of the mask is currently lacking.   A third type of filtering mask is the powered air-purifying respirators (PAPR) or contained air-purifying respirator (CAPR).  These are looser fitting hoods attached to battery-powered units that contain a HEPA filter and produce positive pressure and generate clean air for the wearer.[6,7] These also do not have expiratory protection. 

Extending the Use of Masks

There are several methods to extend use and reprocess otherwise disposable masks and help extend the life of masks in short supply.[4, 6, 7] Storing masks in an air-permeable vessel, such as a paper bag or perforated plastic container, ensures that any moisture accumulated on the mask dries and the pathogens are unable to survive.  There are several methods studied and approved for mask reprocessing.  One is the Battelle method, which utilizes vaporized hydrogen peroxide to sterilize masks and may be repeated multiple times without significant mask damage.[8,9] The STERRAD method uses hydrogen peroxide in plasma form and is a quick and accessible method, but will damage the filter after 3 cycles.[10,11]  UV light sterilization is also effective,[12, 13, 14]  as is dry heat or steam at 70°C.[3,15] The minimum UV dose required to be virucidal is only 1 mJcm2, but some bacteria require up to 41 mJ/cm2.  Higher doses of ultraviolet (UV) exposure may shorten the life and integrity of the straps, worsen the overall fit of the mask, and damage the filter if exposed to over 950 mJcm2.  The use of a UV meter placed outside of the room is necessary to track the UV dosage. Depending on the machine, dosages of at least 300mJcm2 may be encountered following 15 minutes of treatment at which time the UV machine should be stopped.[12]

The steam and microwave steam bag sterilization method depends on the availability of an autoclave and microwave bags, and the treatment time depends on the wattage of the microwave.  Drying time is 30-60 minutes and depends on the mask model.  Each of these methods typically requires significant physical space (such as an operating room or dedicated sterile processing department) as well as time to set up the equipment required to sterilize the masks. It is also essential to expose as much of the mask’s surface area to the treatment, so careful training must take place to ensure high levels of quality control.  Some institutions have created protocols and send their masks out for standardized processing, which can improve efficiency of space but may slow turnaround time. Each institution must weigh the pros and cons and find a solution that works.  It is also possible that none of these methods are accessible, and therefore staff must consider using reusable masks, such as the PAPR, CAPR, and elastomeric masks, which can be decontaminated with germicidal wipes or disassembled and submerged in a diluted bleach or isopropyl alcohol solution and allowed to dry.[16]   The filters that accompany these masks are studied for industrial usage, and the recommendations follow guidelines for heavy vapor usage. Therefore, although the manufacturer will not certify these findings, an evaluation of these filters has determined that acceptable usage is a minimum of 30 days, up to 6 months or when there is more resistance to air flow with normal breathing or if the filter becomes soiled (University of Chicago, Oregon Health & Science University, University of Auckland PPE committees, email communication, June 2020).[16, 17, 18]

Figure 1 includes additional resources about these processes as well as other forms of PPE.

 

 

Figure 1. Further reading

Wearing a Mask and Material Consideration

Cleaning and Reuse

Dry Heat/Steam Sterilization

  • Garcia Godoy LR, Jones AE, Anderson TN, et al. Facial protection for healthcare workers during pandemics: a scoping review. BMJ Glob Health 2020;5:e002553. doi: 10.1136/bmjgh-2020-002553.

Microwave Steam Bags

  • Fisher E, Williams J, & Shaffer R. Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators. PLoS One 6(4):e18585. doi: 1371/journal.pone.0018585

Various Mask Types

  • Garcia Godoy LR, Jones AE, Anderson TN, et al. Facial protection for healthcare workers during pandemics: a scoping review. BMJ Glob Health 2020;5:e002553. doi: 10.1136/bmjgh-2020-002553.

Extended Reuse

  • Bergman MS, Viscusi DJ, Zhuang Z et al. Impact of multiple consecutive donnings on filtering facepiece respirator fit. Am J Infect Control 2012;40(4):375-80. doi: https://doi.org/10.1016/j.ajic.2011.05.003
  • Fisher EM, Shaffer RE. Considerations for recommending extended use and limited reuse of filtering facepiece respirators in health care settings. J Occup Envir Hygiene 2014;11(8)115-28. doi: 10.1080/15459624.2014.902954.
  • Centers for Disease Control and Prevention. Decontamination and reuse of filtering facepiece respirators. Available at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html
  • Centers for Disease Control and Prevention. Operational considerations for personal protective equipment in the context of global supply shortages for coronavirus disease 2019 (COVID-19) pandemic: non-US Healthcare settings. Available at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/non-us-settings/emergency-considerations-ppe.html#.

Elastomeric Mask Usage and Cleaning

Filter Life

PAPR/CAPR Documentation

  • Fisher EM, Shaffer RE. Considerations for recommending extended use and limited reuse of filtering facepiece respirators in health care settings. J Occup Envir Hygiene 2014;11(8)115-28. doi: 10.1080/15459624.2014.902954.
  • Verdict Medical Devices. 2020. MAXAIR CAPR System. Available at: https://www.medicaldevice-network.com/projects/maxair-capr-system/. Accessed June 11, 2020.

NIOSH Approved List

  • Centers for Disease Control and Prevention: NIOSH-approved particulate filtering facepiece respirators. https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/default.html> [Accessed 11 June 2020].

COVID-19 Airway Management Isolation Chamber (CAMIC)

  • S. Food and Drug Administration. Fact sheet for healthcare providers: Emergency use of the COVID-19 airway management isolation chamber. Available at: https://www.fda.gov/media/138216/download

Coverall/Gown Research

Face Shields/Goggles

  • Centers for Disease Control and Prevention. Strategies for optimizing the supply of eye protection. https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/eye-protection.html
  • Iannell D. Seeing eye-to-eye when selecting safety goggles. EHS Today, October 10, 2014. Available at: https://www.ehstoday.com/ppe/eye-face-head/article/21916578/seeing-eyetoeye-when-selecting-safety-goggles.
  • Perencevich EN, Diekema DJ, Edmond MB. Moving personal protective equipment into the community: face shields and containment of COVID-19. 2020;323(22):2252-3. doi:10.1001/jama.2020.7477

References

  1. Johns Hopkins Medicine. Coronavirus face masks & protection FAQs. June 2, 2020. Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-face-masks-what-you-need-to-know. Accessed June 11, 2020.
  2. World Health Organization. Advice on the use of masks in the context of COVID-19: Interim guidance. June 5, 2020. Available at: https://www.who.int/publications-detail/advice-on-the-use-of-masks-in-the-community-during-home-care-and-in-healthcare-settings-in-the-context-of-the-novel-coronavirus-(2019-ncov)-outbreak. Accessed June 11, 2020.
  3. Garcia Godoy LR, Jones AE, Anderson TN, et al. Facial protection for healthcare workers during pandemics: a scoping review. BMJ Glob Health 2020;5:e002553. doi: 10.1136/bmjgh-2020-002553.
  4. Centers for Disease Control and Prevention. NIOSH-approved particulate filtering facepiece respirators. Available at: https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/default.html. Accessed June 11, 2020.
  5. Centers for Disease Control and Prevention. Operational considerations for personal protective equipment in the context of global supply shortages for coronavirus disease 2019 (COVID-19) pandemic: non-US Healthcare settings. Available at: https://www.cdc.gov/coronavirus/2019-ncov/hcp/non-us-settings/emergency-considerations-ppe.html#. Accessed June 11, 2020.
  6. Fisher EM, Shaffer RE. Considerations for recommending extended use and limited reuse of filtering facepiece respirators in health care settings. J Occup Envir Hygiene 2014;11(8)115-28. doi: 10.1080/15459624.2014.902954.
  7. Verdict Medical Devices. 2020. MAXAIR CAPR System. Available at: https://www.medicaldevice-network.com/projects/maxair-capr-system/. Accessed June 11, 2020.
  8. Bergman MS, Viscusi DJ, Zhuang Z et al. Impact of multiple consecutive donnings on filtering facepiece respirator fit. Am J Infect Control 2012;40(4):375-80. doi: https://doi.org/10.1016/j.ajic.2011.05.003
  9. Centers for Disease Control and Prevention. Decontamination and reuse of filtering facepiece respirators. Available at https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html. Accessed June 11, 2020.
  10. Battelle CCDS personal protective equipment (PPE) decontamination for reuse. Available at: https://www.battelle.org/inb/battelle-critical-care-decontamination-system-for-covid19. Accessed June 11, 2020.
  11. Final report for bioquell HPV decontamination for reuse of N95 respirators. July 2016. Available at: https://www.fda.gov/media/136386/download. Accessed June 11, 2020.
  12. Advanced Sterilization Products. Instructions for use for reprocessing N95 masks in STERRAD sterilization systems during the COVID-19 public health emergency. Available at: https://www.mhanet.com/mhaimages/COVID-19/AP-2000011-Instructions_for_Use_for_Reprocessing_N95_Masks_in_STERRAD_Sterilization_Systems%20(5).pdf. Accessed June 11, 2020.
  13. V-PRO external Q&A. Available at: https://www.steris.com/-/media/documents/pdfs/covid19-landing-page/4-10/covid19-n95-and-n95-equivalent-respirator-vpro-decontamination--external-qa.ashx. Accessed June 11, 2020.
  14. Lowe JJ, Paladino KD, Farke JD, et al. N95 filtering facepiece respirator ultraviolet germicidal irradiation (UVGI) process for decontamination and reuse. Nebraska Medicine. Available at: https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdf. Accessed June 11, 2020.
  15. Lindsley WG, Martin SB, Thewlis RE, et al. Effects of ultraviolet germicidal irradiation (UVGI) on N95 respirator filtration performance and structural integrity. J Occup Envir Hygiene 2015;12(8):509-17.
  16. Mills D, Harnish D, Lawrence C, Sandoval-Powers M, Heimbuch, B. 2020. Ultraviolet germicidal irradiation of influenza-contaminated N95 filtering facepiece respirators. Am J Inf Control 2018;46(7):e49-e55. doi:1016/j.ajic.2018.02.018.
  17. Cleaning and disinfecting 3M reusable elastomeric half and full facepiece respirators following potential exposure to coronaviruses. Available at: https://multimedia.3m.com/mws/media/1793959O/cleaning-and-disinfecting-3m-reusable-respirators-following-potential-exposure-to-coronaviruses.pdf. Accessed June 11, 2020.
  18. Wilson R, Cichowicz JK, Casey M. Good clean fun: cleaning considerations for elastomeric respirators. NIOSH Science Blog. Available at: https://blogs.cdc.gov/niosh-science-blog/2019/02/14/v-day-2019/. Accessed June 11, 2020].
  19. Respirator selection. Available at: https://www.3m.com/3M/en_US/safety-centers-of-expertise-us/respiratory-protection/respirator-selection/#:~:text=3M%20recommends%2040%20hours%20of,or%2099.97%25%20of%20airborne%20particles. Accessed June 11, 2020.

 

 

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