Discussion Central

Expand all | Collapse all

M95 mask: sterilize and reuse ? Other PPE, too ?

  • 1.  M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-02-2020 11:54

    2 April 2020    AM
    Juneau, AK

    AIChE Friends,

    Why are we discarding thousands of M95 masks and other PPE, every day in USA, that could probably be simply, quickly, and economically sterilized and reused ?   I've not heard on the news that this apparent option is in use.
    What is AIChE's advice on sterilization and reuse, as described below ?

    1.  Could M95 masks be re-used simply by quickly spraying the exterior of each with "Clorox water" from a compressed- air-powered spray paint gun, or an electric-powered spray paint gun like Wagner ?
    The amount of water sprayed on the mask would be < 100 mg, I suppose, as a very fine mist which would probably not damage the mask, would kill all virus and other pathogens, would dry quickly, allowing immediate reuse thereafter. 
    Both outside and inside surfaces could be sprayed.
    Mask(s) could quickly be stored in a Ziplok bag, for personal reuse.  Perhaps the health caregivers would prefer personal masks, with their name on it, because our culture is averse to sharing in this way.

    Perhaps M95 masks and face shields could be sterilized 20 times or more, without performance loss.  A small Sharpie check mark could be applied to outside of each mask and perhaps other gear, to limit sterilize-and-reuse cycles, if necessary for prudence.
    I understand that "washing" an M95 once could damage its performance and integrity.

    The USDOE national labs could probably quickly research the efficacy, practicality, and methodology for a successful spray sterilization-and-reuse program at any hospital.

    Meantime, hospitals could quickly hire local  auto body shop skilled spray painters who know how to operate spray equipment, to uniformly and effectively apply the Clorox water or other disinfectant, and set them up in underutilized hospital space -- the boiler room or outdoors -- where overspray would be less threatening to the painter and to others.
    Some painters have "active ventilation" systems they could probably move to the hospital.  These provide positive-pressure fresh air from outdoors to a full-face mask.
    Some hospitals already have a compressed air supply to operate the paint spray guns, such as:  https://www.harborfreight.com/32-oz-heavy-duty-multi-purpose-air-spray-gun-69704.html ,     https://www.walmart.com/ip/Campbell-Hausfeld-Pressure-Spray-Gun-AT701100/403918167 ,     https://www.walmart.com/ip/Campbell-Hausfeld-DH420000AV-General-Purpose-Spray-Gun/21270109

    Here's an electrically-powered alternative that requires no compressed air:


    As citizens are encouraged, as in LA,  to wear "face coverings", like masks, whenever they leave home for essentials like groceries, we should encourage them to re-sterilize and reuse these coverings.  Many homes have refillable spray bottles they could use for "Clorox water", though without the very fine misting produced by a compressed air paint spray gun.

    2.  Could other PPE be similarly disinfected for re-use ?   Wash gowns and all fabric components in regular washing machines with the right amount of Clorox in the soap ?  Might get 20+ uses for some of this equipment.

    3.  Have hospitals and caregivers considered an M95 alternative, wearing a spray painting respirator, by 3M and others, which is tight-fitting to the face, has cartridges designed to stop organic solvent molecules smaller than viruses, and could easily be swabbed or sprayed after each shift with "Clorox water" (1/2 cup per gallon) or other disinfectant, and reused ?  Might be better than nothing, if you can get one of these masks.  They are probably scarce, too.  Many might be obtained from citizens and manufacturers, by public announcement and request.
    They might be reused 100+ times.

    I wear my 3M painter's mask, plus workshop tight-fitting safety goggles, when I go to grocery or post office or other gathering places, in case we discover that COVID-19 is spread via simple respiration from the asymptomatic uninfected, leaving such gathering places with a ubiquitous internal cloud of airborne very fine virus-bearing particles which are not gravity settling.


    Our wonderful health caregivers must be "tough".  Let's be sure they don't run our of safe PPE.

    "Toughness" :    In the mid-80's, when USA and the Russians almost blew up the world in the insane nuclear arms race,  my wife, Nancy, and I volunteered in the Beyond War global educational  movement., started by early tech industry people in Palo Alto, CA.
    At a state-of-art satellite TV linkage national meeting among 20+ sites in USA, in about 1985, a Hewlett Packard (HP) exec related to us this story, told to them a few months earlier at an internal management training seminar at HP, by John Madden, recently-retired head coach of the Oakland Raiders :
    " My greatest challenge as head coach of the Oakland Raiders was recruiting:  how to identify which outstanding college football players had the potential to be outstanding pro players; men we would want to recruit for the Raiders.
    My success was not good.  I started with their stats, of course:  strength, speed, weight, points scored, tackles -- all of that.  Correlation with their pro success was puzzling and poor.  I was lamenting my problem with the team psychologist one day, and he said, "Coach, you're looking at the wrong things.  It's mind over matter."  He helped me think differently about recruiting.
    "So, I changed my approach.  Now, when I sit down to talk with an outstanding college football player, at his college, we talk football,  of course.  Then, I steer the conversation to ask about how they deal with disappointment and adversity.  Girlfriends, finances, bad midterm grade in a college course, injury, parents, siblings -- one leads to another.  Those conversations are very helpful, enlightening.  After several years, I've concluded that what I'm  looking for in those ballplayers, those young men, is "toughness".  By that,  I do not mean meanness, or  violence,  or the ability to  inflict or endure pain.  "Toughness" is the ability to see what you don't want to see, hear what you don't  want to hear, and do what you don't want to do -- with enthusiasm.  That's what I look for, now, in those outstanding ball players. And, it works rather well. "
    Our wonderful health care workers are certainly tough, must be tough.  We all have our limits, though.  Thank them for doing your best, today, and for many days to come.  I can only vaguely imagine their plight, and anxiety about PPE. 

    We love them.  Let's protect them and relieve some of their anxiety.


    Bill Leighty
    Director,  The Leighty Foundation  (TLF)
    Principal,  Alaska Applied Sciences, Inc. (AASI)
    Box 20993, Juneau, AK  99802-0993
    907-586-1426       Cell 206-719-5554    

  • 2.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-03-2020 09:55

    Battelle has a technology for sterilizing masks




    Valerie L. Young, Chair

    Department of Chemical and Biomolecular Engineering

    171 Stocker Center

    Ohio University

    Athens, OH 45710

    Phone: 740-593-1492

    e-mail: youngv@ohio.edu

    Pronouns: she / her / hers


  • 3.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-08-2020 11:44

    Thanks, Valerie Young (3 April) and Betsy Blair (7 April).  I'm an EE, not a ChemE, so please forgive my ignorance of appropriate disinfecting liquid formulations and off-shelf products more useful than "Clorox water", as I proposed. 

    Valerie:  Battelle has a technology for sterilizing masks:   https://www.battelle.org/inb/battelle-critical-care-decontamination-system-for-covid19      
    My comment:  This system is for high volume; it is a piece of capital equipment that would take time to manufacture and deploy.  The hospitals need a quick and easy solution, today, for re-use of M95 masks and other PPE.  Wouldn't spraying a small mass, ~ 10 - 100 mg, of very fine droplets of the optimum disinfectant(s) on the surface(s) of masks and other PPE be effective, if done properly ?

    Betsy Blair:    Here is a reference about reusing masks from the CDC that was issued on April 1:    https://www.livescience.com/sanitizing-medical-masks-for-reuse-coronavirus.html    
    My comment:  The nine potential "re-use" methods listed do not include a simple spray from a spray-painting gun, compressed air or electric (Wagner). 

    Should AIChE propose and publish a protocol for spray disinfection, enabling hospitals to quickly mitigate the PPE supply shortage danger ?  See my earlier suggestions for process and equipment. 
    The challenge is probably to apply the right amount (mg) to the outer surfaces, and perhaps also inner surfaces, of masks and other PPE.  Spray painting is a skill; fortunately widely distributed in many auto body repair shops.  Hire them to setup shop in whatever hospital space is available:  boiler room; shipping container in parking lot.

    Thank you.

    Bill Leighty
    Director,  The Leighty Foundation  (TLF)
    Principal,  Alaska Applied Sciences, Inc. (AASI)
    Box 20993, Juneau, AK  99802-0993
    907-586-1426       Cell 206-719-5554    

  • 4.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-03-2020 13:51
    Edited by Monica Mellinger 04-03-2020 15:55

    How about putting them in the microwave for a few seconds?

    Emmett Miller, PE(Ret), FAIChE

    Emmett Miller PE retired, FAICHE
    Lafayette CA

  • 5.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-03-2020 16:38
    Great idea and great philosophy in these times.

    I think I would just run the used masks through the dry cleaners.  Maybe turn up the time and temperature.

  • 6.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-03-2020 17:58



    Thanks.  I seem to recall reading somewhere 2-3 weeks ago that the virus would succumb to microwave radiation.  Heat, alone, might do the job since a recent report indicated that they can live 3-4 weeks in a refrigerator.  BTW, sorry for hitting the wrong key on your name.






  • 7.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-04-2020 18:08
    Another good idea.  Simple solutions for big problems.  Thanks Emmett.

    If the virus can survive long periods in cold temperatures, that's a problem.  

  • 8.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-04-2020 00:03
    • 70 C / 158 F heating in a kitchen-type of oven for 30 min, or
    • hot water vapor from boiling water for 10 min, 
    are additional effective decontamination methods.

    Also: https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html

    Steve Cutchen
    Investigator, retired
    US Chemical Safety Board
    Houston TX

  • 9.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-07-2020 08:34
    Here is a reference about reusing masks from the CDC that was issued on April 1:

    Using a Clorox based sanitizer will remove the static charge in the microfibers in N95 facial masks, reducing filtration efficiency. In addition, chlorine also retains gas after de-contamination, and these fumes may be harmful.

    Betsy Blair
    Director of QA EMEA
    AIB International
    Manhattan KS

  • 10.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-13-2020 21:24

    Hot vapour can be used to sterilize the mask. Boil some water and allow the hot vapor pass through the mask for half an hour.

    Catalina Zurano

    Buenos Aires

  • 11.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-15-2020 15:04
    There will be a lot of "Lessons Learned" from this pandemic, and hopefully we will not forget them for the eventual "Next Time." Which could be in 9 months.
    The N95 masks have an electrostatic factor excited when the inner filter is foamed from poly-propylene at high temperature and pressure.  Attempt to sterilize the masks with ioninzing radiation (a la food processing) did not affect the pressure drop but reduced the effectiveness at stopping 0.8 micron droplets from 95% to 30%, apparently due to the reduction of the static charge.  So, we need to be careful here.

    George Hebbard
    Lithia Technology
    Lithia FL

  • 12.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-16-2020 11:53
    Good to know.  If we keep this up - learning, inventing, and implementing new technology (same thing we've been doing for the past thousands of years), this virus and others to follow will be like minor irritations.  

  • 13.  RE: M95 mask: sterilize and reuse ? Other PPE, too ?

    Posted 04-19-2020 12:15
    What a great discussion. I wanted to share a comment by AIChE member @Joseph Yurko on a recent blog post on ChEnected entitled ChEs Tackle COVID-19:

    Joe shared an amazing story about how a simple dinner conversation between a husband (ChemE) and his wife (a doctor) led to the reuse of 80k masks through a VHP process application. See his comment at the bottom of the post.

    Very Best,

    John Vasko
    Director, Communications & Online Content
    New York NY