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Face Mask Sterilization for Viruses

New information regarding Covid-19, SARS-CoV-2 (the virus that causes COVID-19) and the reuse of N95 masks is being released at an increasing rate. CSS will attempt to update this page in a timely manner to reflect important changes. However, as information is rapidly changing, CSS is not able to guarantee that the information provided here reflects the most current guidance and/or literature.

Important Update: As of 4/1/2020, CDC has released guidance on the decontamination processes for reuse of N95 masks. This information can be found on the CDC website: https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html

With the global Covid-19 pandemic everywhere in the news, many healthcare professionals and concerned citizens are grappling with the shortage of respirator masks, vital tools for ensuring that healthcare workers are not infected by the people they’re trying to help. There has also been a large amount of confusion from the general public about what types of masks are useful for what, as many people are considering wearing masks in public for the first time due to news coverage about the Coronavirus.

In this blog post, we will briefly explain the various types of masks useful for infection control, and the different procedures available to help reduce some of the risk involved with the reuse of masks and respirators. None of the methods found remove all risk associated with mask reuse.

Broadly, there are three different types of masks usable for infection control:

  • Surgical Masks
  • Elastomeric Respirators (1).
  • N95 Type Respirator Masks

Of these three types, only some Elastomeric Respirators are designed for steam sterilization in an autoclave – neither Surgical Masks nor N95 Masks are designed for steam sterilization.

Surgical Masks

Surgical masks (see Image 1) are loose, single use cloth masks designed to provide protection against large droplets, splashes or sprays of bodily or other hazardous fluids. These types of masks experience leakage around the edges when the user inhales, and do not provide a reliable level of respiratory protection against smaller airborne particles. The primary recommended medical function of these types of disposable masks is for infected individuals who want to decrease the risk of transmitting the disease to others in their vicinity, and they are not a substitute for a respirator mask and their primary function is not to protect the wearer of the mask.

In professional healthcare settings, these masks are generally treated as single-use disposable items. As of this writing, we found no published literature regarding decontamination processes of used surgical face masks. It is possible that since they are not meant to protect the user against transmission of air-borne diseases and that are inexpensive enough to be treated as single use disposable items, no studies have been performed on their decontamination for reuse.

 

Image 1: Surgical Mask

 

Recently the CDC has issued guidance (17) regarding the creation and use of homemade layered cloth face coverings that would provide an initial barrier to aerosolized droplets, the primary mode of transport for SARS-CoV-2. Further, the use of a face mask also acts as a deterrent to touching one’s face, another vector for viral infection. This recommendation (18) replaced previous guidance that was intended to preserve masks for those who were at highest risk and needed them most – frontline healthcare workers and those working in public safety. Now that surgical masks and N95 masks are largely unavailable for personal purposes, a recommendation to use cloth face coverings no longer carries this risk. Additionally, some hospitals have begun accepting homemade masks produced by volunteers, and understandably many private citizens are concerned about potentially infecting frontline healthcare workers with homemade masks they create should they turn out to be asymptomatic carriers of the virus (20). The international World Health Organization (WHO) has also issued some guidance regarding the use of cloth face coverings, emphasizing that they should never be used in place of proper hand hygiene and social distancing guidelines (21).

The CDC recommends laundering homemade face masks regularly depending on use. Soap and other liquid detergents are quite effective at inactivating all kinds of viruses (19), particularly with the long exposure times and agitation provided by a standard laundry machine washing and rinsing cycle.

Further down in the blog, we will be reviewing literature currently available regarding decontamination methods available for N95-type respirators. The critical reason for such involved and precise methods for N95 type respirators specifically lies not in the difficulty of inactivating the virus but in attempting to preserve the function of the delicate electrostatic filtration element present in N95 type respirators which will not exist in homemade cloth masks. Immersion in liquid disinfectants and detergents that would severely compromise this N95 filter element is not a concern with homemade masks, which can be soaked through and washed much more thoroughly without damaging the mask or appreciably reducing its effectiveness.”

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