Stanford researchers confirm N95 masks can be sterilized in oven(m.box.com)
m.box.com
Stanford researchers confirm N95 masks can be sterilized in oven
https://m.box.com/shared_item/https%3A%2F%2Fstanfordmedicine.box.com%2Fv%2Fcovid19-PPE-1-1
185 comments
I would suspect if the general population was told to do this we'd have more disruptions due to house fires than from the increased risk of unboxing packages outside of the door, discarding them and then washing your hands and clothes.
What catches fire at 75 Celsius?
I don't think my oven can go lower than 200F.
If you have a thermometer you can turn the oven off manually as it approaches your target temperature. I do this for warming bread dough. Once you know how long it takes you don't need the thermometer.
If your oven is not accurate near 75 C. maybe you can use one of the other methods, from the pdf it looks like water steam could do the same job.
The problem is the assumption that people will consistently manage to ensure it only reaches 75 degrees.
Ironing clothes is 100-250 °C.
Should we just be ironing masks?
Should we just be ironing masks?
I'm confused by all the disclaimers regarding home ovens. WHY NOT a home oven, what is the scientific reason? I've been baking N95s on a tray in our kitchen oven at 170F for ~20-30 min and reusing. These articles seem to suggest that's a bad idea but do not say WHY. Would love to know WHY.
Perhaps just because of the step where you bring the contaminated N95 into your home kitchen and handle it there, before it enters the oven? This sounds tricky to get right.
Do we need the steam bags to pack the n95 respirators? Or is it okay to just put inside the oven.
TIL U+2103 DEGREE CELSIUS and U+2109 DEGREE FAHRENHEIT.
It took me a few passes to realize you were not just being comically excited and typing in all caps, but rather, everything you typed is rather pedantically and accurately capitalized.
I just copied the DuckDuckGo Unicode Instant Answer (https://duck.co/ia/view/unicode) ;)
On Windows ALT+248 (on keypad) makes a degree symbol: °
IMO it looks better than the single glyph. (°C °F vs ℃ ℉)
IMO it looks better than the single glyph. (°C °F vs ℃ ℉)
Unicode agrees:
> Several letterlike symbols are used to indicate units. In most cases, however, such as for SI units (Système International), the use of regular letters or other symbols is preferred.
> In normal use, it is better to represent degrees Celsius “°C” with a sequence of U+00B0 degree sign + U+0043 latin capital letter c, rather than U+2103 degree celsius. For searching, treat these two sequences as identical. Similarly, the sequence U+00B0 degree sign + U+0046 latin capital letter f is preferred over U+2109 degree fahrenheit, and those two sequences should be treated as identical for searching.
(From https://www.unicode.org/versions/Unicode13.0.0/ch22.pdf)
> Several letterlike symbols are used to indicate units. In most cases, however, such as for SI units (Système International), the use of regular letters or other symbols is preferred.
> In normal use, it is better to represent degrees Celsius “°C” with a sequence of U+00B0 degree sign + U+0043 latin capital letter c, rather than U+2103 degree celsius. For searching, treat these two sequences as identical. Similarly, the sequence U+00B0 degree sign + U+0046 latin capital letter f is preferred over U+2109 degree fahrenheit, and those two sequences should be treated as identical for searching.
(From https://www.unicode.org/versions/Unicode13.0.0/ch22.pdf)
The why include the symbols in the first place? Just in case?
It's most likely for round-trip compatibility with another encoding. There are many Unicode codepoints that simply represent combinations of other codepoints. If you don't care about round-tripping, just normalize everything to NFKC or NFKD (the difference being that accented letters like á are one codepoint in NFKC and two codepoints for the base letter and combining mark in NFKD).
For lossless round-tripping with legacy character sets. This is one explicit design goal of Unicode.
So we can make search that tiny bit more complicated.
Does that not appear correctly on your device? Which would that be?
No, it does (a bit squashed, but it's perfectly readable). I didn't know there was as specific Unicode character for those.
As a rule you can just assume there is, no matter the situation.
if you're on a Mac, you can use alt-0 for a degrees symbol too
That's actually U+00BA MASCULINE ORDINAL INDICATOR. You want U+00B0 DEGREE SIGN, which is ⌥⇧8.
Upvoted as one of the most HN comments I’ve ever seen.
I’m generally amused that a top thread for an N95 sterilization post is a Unicode discussion.
What’s the feminine ordinal indicator. I thought it was a degree sign because as a Portuguese speaker I’ve never noticed the feminine ordinal indicator as an easily accessible option. Are both easily accessible on the iOS keyboard?
U+00AA FEMININE ORDINAL INDICATOR is ª, accessible via ⌥9 on macOS.
I just realized I have used the ordinal symbol many times when I should have used the degree sign. Why didn't someone tell me? Oh, I've been making an idiot out of myself.
That depends on the keyboard layout. On the Norwegian keyboard for example, ⌥⇧Q produces the degree symbol, whereas ⌥⇧8 produces U+007B LEFT CURLY BRACKET.
You totally blew my mind—I've been using the wrong one for years. Henceforth, ⌥⇧8. Thank you.
"Conclusions: DO NOT use alcohol and chlorine-based disinfection methods. These 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."
Damn..I've been spritzing mine inside and out with 91% OH...time to bake like Snoop Dogg
Damn..I've been spritzing mine inside and out with 91% OH...time to bake like Snoop Dogg
It still works for killing E Coli (and viruses based on using it on hands).
And you still have at least half of the filtration efficiency. Unsure if that means 90% instead of 95%, or 47.5% instead of 95%, but that's still a gain.
The pressure drop was comparable to the other methods, so you're not going to asphyxiate yourself according to the publication.
And you still have at least half of the filtration efficiency. Unsure if that means 90% instead of 95%, or 47.5% instead of 95%, but that's still a gain.
The pressure drop was comparable to the other methods, so you're not going to asphyxiate yourself according to the publication.
Says 56.33% efficiency after OH bath...too much for me. I too have a Breville Air Oven, and will simply collect a few masks and bake. A few percent efficiency drop is more palatable.
It's interesting that they tried UV light and as far as they know it works for sterilization but they're not sure if it would cause the mask to fall apart eventually. Maybe there's an optimal UV frequency/intensity that kills the virus but doesn't hurt the mask.
> In summary bleach and microwaves were failures at point of care because the bleach gases (skin and respiratory irritants) remained after multiple strategies were used to remove them, the microwave melted the masks and soaking them first led to reduced filtration. EtO, UVGI, and hydrogen peroxide decontamination were safe and effective in the models tested but it is not known if they would retain filtration, material strength,and airflow integrity with repeated use. EtO, UVGI, and hydrogen peroxide limitations include time from decontamination to reuse and available space and materials to decontaminate in an OR setting. 70C /158F 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
> In summary bleach and microwaves were failures at point of care because the bleach gases (skin and respiratory irritants) remained after multiple strategies were used to remove them, the microwave melted the masks and soaking them first led to reduced filtration. EtO, UVGI, and hydrogen peroxide decontamination were safe and effective in the models tested but it is not known if they would retain filtration, material strength,and airflow integrity with repeated use. EtO, UVGI, and hydrogen peroxide limitations include time from decontamination to reuse and available space and materials to decontaminate in an OR setting. 70C /158F 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
The bandwidth ends up being pretty large, so just about any UV light does the trick for most DNA types. Though there are many ways that DNA can UV light interact to make viral DNA mostly unreplaceable, the primary interest is in dimerization. There are a few dimers that will form via UV radiation, each with their own absorption spectra.
I'd just leave things in the sun for a bit. Clouds are transparent to most solar UV too, so just a direct path to the sun is needed. Rotate the objects a few times, maybe take 1.5-2 hours or so.
However, for things that are also UV sensitive, like masks, follow the recommendations when the research has been looked over a bit. Use an oven.
https://en.wikipedia.org/wiki/Pyrimidine_dimer
I'd just leave things in the sun for a bit. Clouds are transparent to most solar UV too, so just a direct path to the sun is needed. Rotate the objects a few times, maybe take 1.5-2 hours or so.
However, for things that are also UV sensitive, like masks, follow the recommendations when the research has been looked over a bit. Use an oven.
https://en.wikipedia.org/wiki/Pyrimidine_dimer
There was a study done using uvc light to disinfect N95 masks and it had negligible effect on filtration rate. It had some effect on strength but that’s only with massive amounts of UVC light. I think you could easily do 50-100 rounds of uvc disinfection without any worries.
My N95 mask smells like burnt plastic after 7 minutes under UVC (254 nm), I wonder if that means the mask is damaged.
Depending on the intensity of light you have and the wattage is the bulb, 7 mins is way too long. If your bulb is very close to the mask 10 seconds is more than enough.
Can I disinfect other things like mail or a cardboard box with a UV light?
Alternatively, would leaving things under the sun have a similar effect and, if so, how long would it take?
Alternatively, would leaving things under the sun have a similar effect and, if so, how long would it take?
UV-C is basically entirely blocked by the ozone layer and doesn't reach the surface of the earth.
Its extremely dangerous, and can cause eye and skin damage with under 60 seconds of exposure, it is absolutely something you do not want to be anywhere around when active.
Its extremely dangerous, and can cause eye and skin damage with under 60 seconds of exposure, it is absolutely something you do not want to be anywhere around when active.
UVC is safest actually. Short wavelength is absorbed by dead skin cells. Never gets to live.
Is there a good reference on how to calculate the time based on the wattage W and distance of the bulb D?
Just want to not 254nm does not kill the virus, it requires 222nm UV-C. Only one manufacturer exists in the US for the bulbs AFAIK.
I wonder if we could vacuum pack the masks and put them in a sous vide, it would be a lot easier to implement than finding enough ovens for all of the masks.
As for the bleach leaving skin and respiratory irritants, maybe hypochlorous acid (HOCl) might be a good alternative?
As for the bleach leaving skin and respiratory irritants, maybe hypochlorous acid (HOCl) might be a good alternative?
I tried this and was not happy with the results
The mask deformed, got wet, and I do not believe the mask got hot enough - it was cool, including the metal parts.
The mask deformed, got wet, and I do not believe the mask got hot enough - it was cool, including the metal parts.
Yes, just make sure you still have good fit. If you put an air bubble in to keep the form, you will need to cook longer to compensate for insulating effects.
FYI. Dr. Larry Chu is an absolutely brilliant person. This should be considered as solid evidence and recommendation.
How is using E. Coli for testing sterilization an accepted protocol? Viruses, even big ones like corona viruses, are much smaller than bacteria. Viruses are very very different than bacteria.They should have tested the sterilization procedure on a virus. Yes, it is harder but lives are at stake.
Escherichia coli is a rod-shaped bacterium. Each bacterium measures approximately 0.5 μm in width by 2 μm in length. Coronaviruses are large pleomorphic spherical particles with bulbous surface projections.[12] The diameter of the virus particles is around 120 nm.
There are 1000 nm in 1 um.
Escherichia coli is a rod-shaped bacterium. Each bacterium measures approximately 0.5 μm in width by 2 μm in length. Coronaviruses are large pleomorphic spherical particles with bulbous surface projections.[12] The diameter of the virus particles is around 120 nm.
There are 1000 nm in 1 um.
It says in the article that (end of page 4)
"4C Air confirmed all the proposed treatments have killed corona viruses."
"4C Air confirmed all the proposed treatments have killed corona viruses."
E. coli are much heartier than viruses and harder to kill. If they kill bacteria they will definitely kill viruses.
Citation was requested: Small viruses like corona viruses have a lipid (fatty) envelope, which is easily compromised. Even more so than large viruses which are non-enveloped. Which in turn are easier to compromise than bacteria [1].
[1] https://www.infectioncontroltoday.com/environmental-hygiene/...
[1] https://www.infectioncontroltoday.com/environmental-hygiene/...
There are two goals here: a) determine whether the mask is damaged by the sterilization technique and b) determine whether that technique actually sterilizes.
The E. Coli experiment is for the latter goal. FWIW, E. coli are a pretty standard way for checking sterilization efficacy. They're easy to culture, fairly hardy, and non-pathogenic. Doing a first pass with live SARS-Cov2 would be incredibly foolhardy (what if the sterilization doesn't work?!)
The E. Coli experiment is for the latter goal. FWIW, E. coli are a pretty standard way for checking sterilization efficacy. They're easy to culture, fairly hardy, and non-pathogenic. Doing a first pass with live SARS-Cov2 would be incredibly foolhardy (what if the sterilization doesn't work?!)
If they used something this size they might resize quickly that N95 isn't suitable, even new ones. Especially for anyone in a high viral load environment.
Weird that alcohol removes the static charge needed for proper filtration, but hot water vapor doesn't. I'm sure someone with a better understanding of electrochemistry could tell us why.
Just guessing that the static charge comes from a coating which is soluble in alcohol but not water.
Wouldn't just leaving the mask alone for say 72 hours decontaminate it? Viruses can't survive for that long, so should be safe to reuse the mask after 72 hours?
The oven method only takes 30 minutes. So masks could be sanitized and turned around for reuse much more frequently than leaving the mask “out of commission” for several days would allow.
The report also found acceptable (if a bit lower) sterilization from applying steam from boiling water for just 10 minutes, which would improve turnaround rates even further.
The report also found acceptable (if a bit lower) sterilization from applying steam from boiling water for just 10 minutes, which would improve turnaround rates even further.
What about other germs, esp from the doctors' own breath? Doctors in OR need sterile masks and hopefully they don't reuse in that setting. But outpatient clinics and testing sites, sure reuse is better than shutting them down due to shortage of respirators.
This is basically what I'm doing with a box of FFP3 masks I bought years ago and partly used. I only need to go out once or twice a week at most, so I can rotate through them and give each mask a good ~14 day rest.
IIRC, there were still traces of the virus on the diamond princess 15 days after it was cleared out. So it might be able to last longer.
The authors of that article specially mentioned their work on the princess would get badly reported - and it was. There was no live cornovirus found. Their were traces of RNA (ie, after the virus was killed some of its body parts lying around).
It's a half-life thing. If your equipment is sufficiently sensitive, you could find remaining virus for a long time. Especially if the conditions are right.
Right. People like to think of things like 'sick' and 'healthy' but maybe it's more subtle than that. Things aren't 'clean' or 'dirty' w COVID, but somewhere on a long spectrum.
Yup, it's continuous, not discrete.
My running joke with the "up to 3 days" figures people keep sharing is that you could get infected "up to 3 miles away" by someone sneezing if the winds/temperatures are just right and you're EXTREMELY unlucky.
My running joke with the "up to 3 days" figures people keep sharing is that you could get infected "up to 3 miles away" by someone sneezing if the winds/temperatures are just right and you're EXTREMELY unlucky.
There's also a distinct probability that your pencil will suddenly levitate an inch then drop back. I'm not kidding.
Next you’ll try to convince me that the moon can pull stuff from the earth towards it.
There's a small probability it'll stop doing that ;)
No, the 15 day thing was viral RNA, rather than live virus.
In the same way, you can find an identifiable skeleton, even after the person is dead.
In the same way, you can find an identifiable skeleton, even after the person is dead.
The story I saw saying this was referring to traces of the virus's RNA, not active virus particles. More like footprints
[deleted]
No, SARS-CoV-2 is thought to have a half-life of about 72 hours on some surfaces but some virus particles can survive much longer.
(edit: that's not right, the half life is shorter with the virus still infectious on a surface for 72 hours or so)
https://www.youtube.com/watch?v=JNQUHc8wbRc
(edit: that's not right, the half life is shorter with the virus still infectious on a surface for 72 hours or so)
https://www.youtube.com/watch?v=JNQUHc8wbRc
That video gives half lives of 5.6 hours for stainless steel and 6.8 hours for plastic, not 72 hours.
72 hours is the time it gives for the virus still being detectable/viable on those surfaces, which is different than the half life.
72 hours is the time it gives for the virus still being detectable/viable on those surfaces, which is different than the half life.
You're right, I misremembered the video. Still, 72 hours as the time when the last virus particle probably dies still seems a bit risky.
It would, but then you need multiple masks per person if each person uses theirs for 1 day. And even that can be a stretch: once they become moist, they're useless.
How moist? They will contain moisture from any use.
True, and they're not cracker dry to start. But if the pores get clogged with water (just like breathing on a cold window), you're hosed.
I was thinking the same. Or keeping it in very dry environment that desicate the virus?
Coronavirus survived for over a week on that empty cruise ship.
It's frustrating that my local hospital is facing a critical shortage of masks, begging for donations -- and there is absolutely no way they will implement this.
They could have people manning the ovens in the cafeteria rotating these things in and out, but wether its fear of liability, "not invented here syndrome", or the idea just sounding crazy, it's not going to happen.
I passed it around to some contacts who work there anyway, but I have no hope.
They could have people manning the ovens in the cafeteria rotating these things in and out, but wether its fear of liability, "not invented here syndrome", or the idea just sounding crazy, it's not going to happen.
I passed it around to some contacts who work there anyway, but I have no hope.
What is the source on this? Sure it has Stanford medicine stamped all over it, but that is no proof. To be clear I'm not saying anything in it is wrong just wondering why it's hosted on Box.
Fantastic! Thank you for linking this.
Does this work for surgical masks as well? Are they actually comparable in filtration size to N95? I need to look up all the values...
Edit: from cdc guidelines:
>SARS appears to be transmitted mainly through direct contact with infectious materials (including large respiratory particles), and surgical masks will provide barrier protection against droplets that are considered to be the primary route of SARS transmission. However, surgical masks may not adequately protect against aerosol or airborne particles,
Presumably as coronaviruses SARS and COVID19 are similarly sized, and I don't know that the aerosolization of COVID19 has been confirmed. So at least in a casual setting like stores I imagine masks should reduce the probability of inhaling viral particles.
Edit: from cdc guidelines:
>SARS appears to be transmitted mainly through direct contact with infectious materials (including large respiratory particles), and surgical masks will provide barrier protection against droplets that are considered to be the primary route of SARS transmission. However, surgical masks may not adequately protect against aerosol or airborne particles,
Presumably as coronaviruses SARS and COVID19 are similarly sized, and I don't know that the aerosolization of COVID19 has been confirmed. So at least in a casual setting like stores I imagine masks should reduce the probability of inhaling viral particles.
Surgical masks have an air gap, so are not comparable to N95 masks at all in that regard. They are solving different problems.
Every time I left my apartment unit to take out the trash or pickup a delivery, I've thrown all the outerwear I wore into my steam / dry cleaning machine:
https://www.lg.com/us/styler-steam-closet
It's relatively effective according to this article
https://www.lg.com/us/styler-steam-closet
It's relatively effective according to this article
The dutch are doing it with hydrogen peroxide in their official recommendations https://www.rivm.nl/en/documenten/reuse-of-ffp2-masks
It seems to me that a canning pressure cooker would do a faster and better job of sterilizing than an oven. up to 250 + degrees F at twenty pounds pressure. Available at most hardware stores, home depot, fleet farm etc. 22qt size would do a lot of masks
Anyone know if this method works with the disk filters you put on the half face mask?
https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-...
https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-...
What about just waiting for the virus to be inactive then reusing the masks? I haven't found any general consensus, but I've read reports of COVID-19 staying infectious on objects ranging from 1 day to 9 days. If a rotation of masks are used, then there would be no need for washing or baking, which also avoids damaging the microfibers or removing the static charge in the masks.
Here's a study on the surface lifetime of SARS-Cov-2: https://www.nejm.org/doi/10.1056/NEJMc2004973
That seems like it'd be much harder to manage. Given the uncertainty about how long the virus takes to inactivate, you'd have people juggling at least a dozen N95 respirators with varying amounts of contamination.
A quick disinfection protocol with greater certainty seems preferable.
A quick disinfection protocol with greater certainty seems preferable.
It is not whether you can but whether you have a safe and sterile procedure to do so. Wearing mask is symbolic and protect both sides a bit. But as said it is also meant if you touch the germ on the mask etc. you still can be infected. Now how are you going to protect yourselves if you reuse your mask and what procedure involved, if it can be recycled.
From the fine article:
> IMPORTANT NOTICE
> Do not use anything in your home to disinfect contaminated
> equipment. Please do not heat your masks in a home oven!
> IMPORTANT NOTICE
> Do not use anything in your home to disinfect contaminated
> equipment. Please do not heat your masks in a home oven!
Alternative method - how about putting the masks in a box with an ozone generator? Comments?
Dangerous and it degrades them.
If this indeed is the case, anyone with low-temp ovens should immediately be volunteering them up to help sterilize. Hell, I have two of them the Breville countertop convection oven - It'll go as low as 120F steadily, so 158F should be no problem.
Forget home ovens. Hospitals are surrounded by restaurants with big, roomy commercial ovens, most of which are now closed. A functioning government could commandeer those ovens for sterilization.
Heck, pay the restaurant owners rent to use them — now you’ve solved two problems.
Heck, pay the restaurant owners rent to use them — now you’ve solved two problems.
I doubt you'd want what is essentially medical waste burning off inside a commercial food oven.
As opposed to peoples’ home ovens?
Heck, tell the restaurateurs that when we’re done using their ovens we’ll rip them out and install shiny new ones. Problems that can be solved by throwing money at them are good problems to have right now.
Heck, tell the restaurateurs that when we’re done using their ovens we’ll rip them out and install shiny new ones. Problems that can be solved by throwing money at them are good problems to have right now.
Why is there presumed to be an oven shortage at all?
Much more need for an average oven every day than face masks, or ventilators.
Hardware stores have plenty of electric ovens stocked, it's not like people have been or will be panic-buying them.
Hospitals have ovens anyway, the ones in their cafeteria kitchens if nothing else. But even if that weren't the case, they could just send somebody to a local store and buy one. They could have it purchased, installed and operational by the end of the day.
Hospitals have ovens anyway, the ones in their cafeteria kitchens if nothing else. But even if that weren't the case, they could just send somebody to a local store and buy one. They could have it purchased, installed and operational by the end of the day.
Most of the food they cook in them is pathogenic and not sterile to begin with...
But I'd still agree with you.
A residential clothes dryer isn't that much cooler than the temperatures they target in this study. Just use a rack or turn off tumble (if you can).
But I'd still agree with you.
A residential clothes dryer isn't that much cooler than the temperatures they target in this study. Just use a rack or turn off tumble (if you can).
I dunno about typical commercial ovens, but the ovens at a pizza place go up to about 800F. it's unappetizing to think about, but I don't think any pathogens can survive for long at that temperature. the real trick might be keeping the oven at a steady low temp to sterilize the masks. they're not really designed for that.
The manager: what are you all cooking?
Employees: N95 masks sir
Customer: can I also order one?
Employees: N95 masks sir
Customer: can I also order one?
And Sauna could work too.
I'm really curious if you'd get the same results if you put the mask in a bag and sous vided it.
People could do that on their stove with a pot of water and a thermometer.
People could do that on their stove with a pot of water and a thermometer.
A lot of regular kitchen ovens can go as low as 100F or 120F. They’re wildly inaccurate and you need to have a baking sheet or other barrier between the mask and any heating elements to block IR.
Source: by far the easiest way to fix crystallized honey is to bake it somewhere in the 120F to 140F range for an hour or two. All the Internet guides saying to use warm water have probably never tried to put a half-full bottle of honey in water, fully submerged to get all the crystals, and without destroying the label. In contrast, all common bottle plastics and labels are just fine in 140F dry air.
Source: by far the easiest way to fix crystallized honey is to bake it somewhere in the 120F to 140F range for an hour or two. All the Internet guides saying to use warm water have probably never tried to put a half-full bottle of honey in water, fully submerged to get all the crystals, and without destroying the label. In contrast, all common bottle plastics and labels are just fine in 140F dry air.
I use the water method, who cares about the label? To keep honey from getting crystals just drink more tea.
I find that the water method results in crystals staying on the sides of the bottle that we’re above water. These serve as nucleation sites to recrystallize the honey faster.
And the label is nice if you have lots of varieties of honey :)
And the label is nice if you have lots of varieties of honey :)
The pressure of the water on your bag might deform the mask though.
My 3M P95 masks (purchased for 2018 Camp Fire smoke) come in compressed bags. Also if you sous vide using vacuum sealer bags (e.g. Foodsaver) those are a little more stiff.
This might not be in good taste but this line of discussion is just hilarious to me.
A $50 electric oven is probably enough for a few hospitals. No need to go searching it.
What kind of hospital doesn't have half a dozen autoclaves?
They tried autoclaves and it destroyed the masks.
Food dehydrators may also work well for this. They usually range around 90-140f.
Many of them have stackable horizontal racks which may make it possible to 6-12 at a time.
edit: s/vertical/horizontal/
Many of them have stackable horizontal racks which may make it possible to 6-12 at a time.
edit: s/vertical/horizontal/
I wonder if the airflow would risk spreading the virus.
Yes, I plan to use mine outside.
Food dehydrators can go lower temperature.
I got a digital toaster over to try this at home, but the lowest temp I can set is 200 degrees F. Can I still use it (with a shorter period)?
Tl;DR: 70C /158F heating in a kitchen-type of oven for 30min, or hot water vapor from boiling water for 10 min, are effective decontamination methods.
Is there a way to configure an autoclave to work at such low temperatures?
According to the document, using an autoclave failed.
> Authors found decontamination using an autoclave, 160C dry heat, 70% isopropyl alcohol, and soap and water (20-min soak) caused significant degradation to filtration efficiency.
> Authors found decontamination using an autoclave, 160C dry heat, 70% isopropyl alcohol, and soap and water (20-min soak) caused significant degradation to filtration efficiency.
https://www.youtube.com/watch?v=0QKnqD7scI4 might be of interest.
I'd think an autoclave/pressure cooker/rice steamer would have a much lower risk of melting plastic fibers in masks since they're physically limited to lower temperatures than a typical oven.
I'd think an autoclave/pressure cooker/rice steamer would have a much lower risk of melting plastic fibers in masks since they're physically limited to lower temperatures than a typical oven.
Yes, most have a low-temperature cycle and the rest can often be configured to include the option.
I think some saunas can get to that temperature.
Water vapor from boiled water seems much easier
I'm skeptical about that. You can easily put a bunch of masks in an oven at one time. There is no complication at all to that approach and no questions of coverage or distance (did your water vapor get all over the mask properly and at a high enough temp). The oven is fire and forget, pull after 30 minutes.
The oven is safer and easier by a wide margin.
The oven is safer and easier by a wide margin.
Well I've thought of using something like "stainless steel steamer". Usually if properly distanced, it is heated uniformly.
In asian area it's not common to have oven but steamer usually available
In asian area it's not common to have oven but steamer usually available
I'm curious why UV light couldn't be used, or even X-ray machines, or one of those "gamma knife" machines.
Is the resulting mask totally sterilized that it could be used without issue by a different person?
From a virological POV, yes. But masks conform to the wearer's face. There's a clip and it can only bend so many times. Not sure if the filter itself also conforms over time.
Users are tested for fit, but that test is based on new masks.
Users are tested for fit, but that test is based on new masks.
Does anyone know if this applies to the N95 masks with a cool vent?
Is there a method if an oven is not available? In a bag in a microwave?
The article mentions microwaves melting the masks.
Microwaves work by heating the water in food. They don't work properly on paper.
The dryer is a much better alternative.
The dryer is a much better alternative.
Not an expert, but I'd be wary of using a microwave at least for the plastic type filters. If the plastic filter fibers absorb microwaves, it might turn out that the smaller fibers get melted without affecting the bulk structure enough to easily notice.
A steamer on a stove seems like a safer bet.
A steamer on a stove seems like a safer bet.
There is a metal clip on the respirator for fitting.
check the last article I submitted.
Flagged this in hope of a more reliable source than a PDF in Box.
Well, apparently source Stanford App uses Box, link appeared in Reddit:
https://stanfordmedicine.app.box.com/v/covid19-PPE-1-1
[deleted]
Sterilize? Sure. But after it the mask won’t be able to filter on N95 level.
Slide 5 says it's fine.
I'd doubt it's sterilized though. Fungal spores will survive this process. But it'll kill viruses: high heat is often good enough.
Keep in mind that N95 is made from polypropylene, which is an autoclavable plastic.
Sterilization is overkill anyway: N95s aren't sterilized from the factory in the first place.
I'd doubt it's sterilized though. Fungal spores will survive this process. But it'll kill viruses: high heat is often good enough.
Keep in mind that N95 is made from polypropylene, which is an autoclavable plastic.
Sterilization is overkill anyway: N95s aren't sterilized from the factory in the first place.
Was interesting reading all the 1-star reviews on AMZ complaining the packaging wasn't sterile (a bread tie,wtf) then complain the straps didn't fit their ears...
>Slide 5 says it's fine.
no, slide 5 says that they suffer at minimum a 3.4% loss in efficiency.
a brand new N95 is still superior.
So, afterwards, you have a sub-par N95 mask that now has increased risk of fungal spores and other hardy pathogens.
no, slide 5 says that they suffer at minimum a 3.4% loss in efficiency.
a brand new N95 is still superior.
So, afterwards, you have a sub-par N95 mask that now has increased risk of fungal spores and other hardy pathogens.
Has this been checked on Snopes.com?
This was "fact checked" weeks ago as false (lol)
https://factcheck.afp.com/novel-coronavirus-health-experts-w...
https://factcheck.afp.com/novel-coronavirus-health-experts-w...
The fact check is obviously incorrect. But note that this research also considers "baking" in oven at 70 celsius for 30 min, and other tests.
My point is that so-called "fact checking" here was incorrect.
> Dr. Ho Pak-leung, a microbiologist and director of the Centre for Infection at the University of Hong Kong, described the video in the misleading post as “fake news” in an email to AFP on January 30.
In a mask shortage the question of whether masks can be sterilized and reused should never have been dismissed out of hand.
We have medical professionals working without masks as we speak due to the shortage.
Many of our trusted experts have been feeding us misinformation exacerbating the problem.
> Dr. Ho Pak-leung, a microbiologist and director of the Centre for Infection at the University of Hong Kong, described the video in the misleading post as “fake news” in an email to AFP on January 30.
In a mask shortage the question of whether masks can be sterilized and reused should never have been dismissed out of hand.
We have medical professionals working without masks as we speak due to the shortage.
Many of our trusted experts have been feeding us misinformation exacerbating the problem.
How is that the same? This is steaming
Yeah the fact check is about steaming (which is totally unrelated and closer to autoclaving, which doesn't work)
Critically, this was tested with E. Coli, NOT a coronavirus. This method has not been proven effective for the current epidemic.
Critically?
> 4C Air confirmed all the proposed treatments have killed corona viruses. Labs have no way to test COVID-19 directly and as an accepted protocol, E. Coli is used for testing. We asked what methods can be used to decontaminate the facial mask for reuse safely and without loss to filtration efficiency. 4C Air confirms using 70 degree C hot air in an oven (typical kitchen-type of oven will do) for 30min, or hot water vapor are additional effective decontamination methods.
Please don't cherry pick here.
> 4C Air confirmed all the proposed treatments have killed corona viruses. Labs have no way to test COVID-19 directly and as an accepted protocol, E. Coli is used for testing. We asked what methods can be used to decontaminate the facial mask for reuse safely and without loss to filtration efficiency. 4C Air confirms using 70 degree C hot air in an oven (typical kitchen-type of oven will do) for 30min, or hot water vapor are additional effective decontamination methods.
Please don't cherry pick here.
Keep reading:
"4C Air confirmed all the proposed treatments have killed corona viruses. Labs have no way to test COVID-19 directly and as an accepted protocol, E. Coli is used for testing. We asked what methods can be used to decontaminate the facial mask for reuse safely and without loss to filtration efficiency. 4C Air confirms using 70 degree C hot air in an oven (typical kitchen-type of oven will do) for 30min, or hot water vapor are additional effective decontamination methods. Please see Table 2"
Is there a temperature range that viruses generally die off within? Assuming yes, it would seem a bit peculiar to have to test a specific virus with a specific temperature, no?
Not at all!
Viruses come in many shapes and forms. One of the major features of viruses is whether they have a viral envelope (derived from the host plasma membrane lipid bilayer) or a protein capsid shell.
The structure of capsids can make them more or less hearty.
Luckily for us, Covid-19 and coronaviruses in general have viral envelopes. These are easy to disrupt with soap and susceptible to the environment.
Polio, on the other hand, was damned near impossible to be rid of. Capsids can be resilient.
Other major features are the nucleic acid family (RNA or DNA), encoding (single or doubly stranded, multiple senses), and these impact mutation rate and what host or viral machinery is used. RNA doesn't survive as long as DNA, but that doesn't matter if the virus is in a good environment.
Viruses come in many shapes and forms. One of the major features of viruses is whether they have a viral envelope (derived from the host plasma membrane lipid bilayer) or a protein capsid shell.
The structure of capsids can make them more or less hearty.
Luckily for us, Covid-19 and coronaviruses in general have viral envelopes. These are easy to disrupt with soap and susceptible to the environment.
Polio, on the other hand, was damned near impossible to be rid of. Capsids can be resilient.
Other major features are the nucleic acid family (RNA or DNA), encoding (single or doubly stranded, multiple senses), and these impact mutation rate and what host or viral machinery is used. RNA doesn't survive as long as DNA, but that doesn't matter if the virus is in a good environment.
So we're accepting E.coli as a benchmark here, because we're pretty sure it destroys the viral envelope?
Why is this more than a guesstimate? It strikes me as odd to test for virus disinfection by using a bacteria, but I am a complete noob in this field.
Why is this more than a guesstimate? It strikes me as odd to test for virus disinfection by using a bacteria, but I am a complete noob in this field.
You did read the author's qualifications, did you not?
Consider your qualifications, ('I am a complete noob in this field.') compared to theirs.
Amy Price, DPhil (Oxon) ... earned her Doctorate in Evidence Based Health Care at The University ofOxford.
Larry Chu, MD, MS (Epidemiology) ....
If anyone understands the science, and the limitations of their study, it is themselves and they caveated their conclusions carefully.
Is it peer reviewed? No. But it is the best science we have at the moment.
A noob in the field isn't going to find a hole in two minutes that two serious professionals haven't thought about.
Consider your qualifications, ('I am a complete noob in this field.') compared to theirs.
Amy Price, DPhil (Oxon) ... earned her Doctorate in Evidence Based Health Care at The University ofOxford.
Larry Chu, MD, MS (Epidemiology) ....
If anyone understands the science, and the limitations of their study, it is themselves and they caveated their conclusions carefully.
Is it peer reviewed? No. But it is the best science we have at the moment.
A noob in the field isn't going to find a hole in two minutes that two serious professionals haven't thought about.
I'm not asking, because I don't trust that this is the best information we have. I am asking, because I want to understand more about how certain the people who understand the subject are about this recommendation.
I thought we (as a computer science-centric population) valued learning over credentials?
I didn't mean to come off as agressively taking a stance, which is /why/ I wrote that I don't know anything about this topic.
I thought we (as a computer science-centric population) valued learning over credentials?
I didn't mean to come off as agressively taking a stance, which is /why/ I wrote that I don't know anything about this topic.
They carefully caveated their results, and we all know this isn't peer-reviewed or replicated--although it has been informally reviewed by other scientists.
But it is also very safe to say that serious scientists don't put forth studies that someone completely uncredentialled can poke a hole in with two minutes of thought.
But it is also very safe to say that serious scientists don't put forth studies that someone completely uncredentialled can poke a hole in with two minutes of thought.
Read the article completely or the comments. Your question has been addressed multiple times in this thread.
So, I tried reading quite a bit of the comments, and the whole article before commenting.
I might have misunderstood the wording:
"4C Air confirmed all the proposed treatments have killed corona viruses. Labs have no way to test COVID-19 directly and as an accepted protocol, E. Coli is used for testing."
I understood this as: There has been no testing using corona viruses (because there's no way to do so currently?), but instead they're benchmarking with E. coli.(because this has some sort of similar attributes)
But what it's saying is(?): Testing has been done on E.coli AND corona viruses, but there's no standardized protocol for corona viruses, which is why they're focusing on the E.coli aspect.
Please do not assume malintent, even though I know these are stressful times, and we'd do well to let important information surface to the general population, I think a part of that is to understand the limitations of that information as well.
I might have misunderstood the wording:
"4C Air confirmed all the proposed treatments have killed corona viruses. Labs have no way to test COVID-19 directly and as an accepted protocol, E. Coli is used for testing."
I understood this as: There has been no testing using corona viruses (because there's no way to do so currently?), but instead they're benchmarking with E. coli.(because this has some sort of similar attributes)
But what it's saying is(?): Testing has been done on E.coli AND corona viruses, but there's no standardized protocol for corona viruses, which is why they're focusing on the E.coli aspect.
Please do not assume malintent, even though I know these are stressful times, and we'd do well to let important information surface to the general population, I think a part of that is to understand the limitations of that information as well.
In a conventional oven, 75 ℃ / 167 ℉ for 30 minutes is sufficient to inactivate SARS-CoV-2. If someone were worried about packages, mail or objects being contaminated, placing them into the oven like this would probably work if allowed to reach that temp internally for that time.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3078131/