Well, this is an unusual question. On a forum discussing the lack of face masks for our medical community, there was a list of possible methods of sterilization. One post said to seal it in a bag and sous vide it. But there was no further instruction. For all I know he could have been being sarcastic, and there was no follow up. But the idea intrigued me, and it certainly could be relevant now. Any comments, suggestions? Temperature, time?
Pasteurisation is not sterilization. You would need to know the maximum temperature at which the virus can survive without a host.
Good point @Ember
After reading your comment I went out and found the following on the World Health Organization site…
“Heat at 56°C kills the SARS coronavirus at around 10000 units per 15 min (quick reduction).”
Based on this I’d think that bagging something up at 60°C for a couple hours should do the trick. Any virologists here in the forum???
That’s a timely question Dru. It also leads me to question why is America unable or unwilling to lead in combating the current COVID-19 pandemic crisis?
The combined shortage of masks with overloaded reprocessing staff and equipment presents a significant challenge to healthcare organizations. However disposable masks are excessively difficult to decontaminate and sterilize.
The SV technique’s vacuum packaging could be effective for the flat surgical style of masks only if packaged in a single layer or two, but it’s slow, has limited capacity, and it’s space intensive.
SV sterilization would be inappropriate for the important formed respirator style N95 masks required for protective use with close Patient contact. Its critical custom-fitted shape would be damaged by SV’s vacuum packaging.
Gas sterilization techniques might be a last resort for some facilities if masks become a higher priority than Patient treatment items.
In contemporary hospital reprocessing facilities delicate reusable items can be effectively sterilized using pressure-less ambient temperature O3 / hydrogen peroxide sterilizers if they have them. Unfortunately most don’t.
Perhaps at some time soon the American public will demand an intensive high-level investigation into the systematic reduction in the number of American hospital beds in service per capita over an extended period of time.
Yes, regularly high occupancy levels enable hospitals to be more profitable. Should that be an appropriate criteria for setting healthcare capacity levels under high demand situations considering the increasing frequency of world-wide viral epidemics, disasters, and catastrophes?
Let’s work together to make things better. Keep well all.
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Stanford Medical reported (from a secondary source 4C Air) that “…using 70 degree C hot air in an oven (not your home oven) for 30min, or hot water vapor are additional effective decontamination methods.” mask-ppe-EBM-v1.2-3-25-20.pdf - Box (pg. 5).
Granted that home ovens may not be calibrated as well as lab ovens, but doing this at home would be better than doing nothing, I would think. I have been re-using my N95 mask without any method of sterilization other than letting it hang in an unused room for a couple of days. I have also been trying to make a homemade face mask to use with my N95, but if I’m not the world’s worst sewer, I must be close.
By far, I think the more unforgivable sin in this crisis has been the lack of personal protective equipment for health care workers. This is the fault of hospital administrators who failed to plan (isn’t that what they get paid for?) as well as government, both state and federal, who failed to plan for a pandemic. Everywhere health care workers are being asked to reuse (up to 5 times in most cases) their N95 masks. Workers are being instructed not to wear PPE, especially masks, in treating some patients, so that they can be saved for treating the most critically ill. I also think it has been wrong for the medical experts to discourage face mask use by the general community. There’s plenty of evidence that transmission of viruses is hindered by the use of a mask. While there is less evidence that a mask can prevent you from getting a virus, that’s probably because there cannot be an ethical clinical study to evaluate the outcome of providing masks to a community and exposing them to a virus. A leading infectious disease expert in China said that is the main mistake Europe and the U.S. have made in this crisis - not wearing masks.
I’m getting way off topic here, so I’ll get off my soap box. But thank you for responding about sous vide for sterilizing a face mask. I may test seal one of my only two N95 masks to see what would happen to it under the sealing pressurization. They’re pretty sturdy, so the shape may spring back.
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I wonder if anyone has even given any thought to irradiation of medical equipment in order to sterilize for reuse. It would be safe, and really the only negative I see is public perception. Perhaps this would take too long and not be feasible to implement at this time, but with the proper setup you should be able to load up a shielded room with everything you need sterilized, zap it good, and be able to safely reuse protective gear - at least in emergencies where sufficient PPE is not available. Maybe there is a flaw to this approach of which I am unaware, but somebody had best start thinking outside the box about this problem. (Stepping down off my soapbox now.)
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Ultra-violet rays are also an effective virus killer as in good old sunshine.
UV is certainly used for steralizing water towers for large air conditioning units.
Hi @CeliaT
Actually UVC light does inactivate viruses. I believe the best wavelength is usually considered to be around 260 to 265 nanometers. And it is something that I think they’ve started to pilot test as a way of sterilizing medical protective gear for reuse due to the shortage. So UV is definitely an option to consider. (But beware of some scammers selling “UV lights sterilizers”. A lot of fakes are being peddled right now.)
My suggestion of using gamma radiation or something similar irradiation method is because it is penetrative, so you need not ensure that the entire surface to be sterilized be exposed. A big underground shielded room could be filled with gear to be sterilized then given a big ZAP of radiation. This would leave no radioactive particulates, but I’m pretty sure it would inactivate any of viruses.
I may be wrong. Perhaps there’s some problem with this method of which I’m not aware as it’s not my field of expertise…but the approach seems viable. I’m just hoping that someone knowledgeable has at least considered it. It’s radical enough that perhaps it hasn’t.
Dru, agreed that wearing a face covering can reduce transmission, but not totally. However, it appears to me that the main mistake made the USA and Europe has been ignoring personal isolation by the general public until it was too late. Masks aren’t required when isolated.
FYI, in the USA the Joint Council of Hospital Accreditation requires and regularly inspects all hospitals’ pandemic plans including required segregated PPE supply storage. With just 2.5 hospital beds per 1,000 citizens in America, it’s far below the typical number in comparably advanced countries like; France, South Korea, or even Canada, where the number is about 6.5 beds per 1,000. Adequate healthcare support planning is simply matching supply with demand, particularly in times of crisis.
Protect yourself and your family, keep well.
Mirozen, no bagging needed to safely sterilize masks for reuse at home.
Consider using your kitchen oven but go a little higher, 75ᴼC to 100ᴼC for 30 minutes for total kill. You may need to get a roll of elastic strap at Walmart’s craft department as the heat will reduce the strap’s elasticity. They are easy to replace using a stapler.
This virus isn’t going to simply disappear soon as some have said. You may not be leaving home without gloves and a mask for a couple of years. And a pocket bottle of sanitizer spray if you can find or make one.
Good luck getting elastic anywhere. Everyone is using it for masks, most of which are being donated to health care workers. Personal isolation is key, but people still need groceries, prescriptions. And here in good ol’ Texas, the governor has allowed church groups to congregate, and nearly every other business is deemed “essential” so it can stay open for business.
I have read on many reputable sites that UV-C does indeed kill viruses.
I have read the same. But I have also read that UV light, including direct sunlight, degrades the protective outer layer of the N-95 mask. Go figure.
I do not know. But even if that is wrong, UV-C, from my understanding, kills only surface organisms. That means it would not kill virus below the surface of the mask. Heat, on the other hand, should.
Hey Dru, here’s a useful clip with information to forward to your governor so he might consider the selfish harm to Texans he is encouraging. The sooner we arrest America’s farewell tour the better it will be for those who survive.
There’s a wealth of science based useful information at the Peak Prosperity web site.
I suspect the temperature needed to kill virus in sous vide or oven would damage the mask.
What nurses are being told to do is put the used mask in a paper lunch bag, and let it dry for at least 48 hours, preferably 72 hours. Drying out kills the virus.
I posted this above @jmack03, but the thread has gotten a little long so you missed it. (And yes, drying does sound like an excellent method.)
The following is from the World Health Organization site…
“Heat at 56°C kills the SARS coronavirus at around 10000 units per 15 min (quick reduction).”
I think it is dangerous to assume SV pasteurisation will disinfect the masks. At best only vegetative bacteria will be destroyed and I’m not sure of the time/temp requirements are for viruses. Also moist heat is required for heat transfer in a dry mask. At work we have to use autoclaves at 121C for 15 min (15 psi pressure). For my CPAP mask and equipment I use a portable ozone generator. If the medical mask was sealed in a plastic bag and filled with ozone, sterilisation would be probably be achieved.
Online its is recommended to spray mask with saline solution then microwave (800W) for 1 min. Should be used for your own mask only and masked should not be shared. Microwave should be dedicated for this purpose only.