14 ms·
Stanford researchers confirm N95 masks can be sterilized in oven
- gshdg 7y agoCritically, this was tested with E. Coli, NOT a coronavirus. This method has not been proven effective for the current epidemic.
- Karrot_Kream 7y agoCritically? > 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.
- toptal 7y agoIs 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?
- echelon 7y agoNot 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.
- NegatioN 7y agoSo 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.
- compiler-guy 7y agoYou 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.
- NegatioN 7y agoI'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.
- compiler-guy 7y agoThey 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.
- ebrenes 7y ago
- 1-6 7y agoKeep 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"
- notRobot 7y agoTl;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.
- dguaraglia 7y agoIs there a way to configure an autoclave to work at such low temperatures?
- milksteak42 7y agoYes, most have a low-temperature cycle and the rest can often be configured to include the option.
- bacon_waffle 7y agohttps://www.youtube.com/watch?v=0QKnqD7scI4 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.
- notRobot 7y agoAccording 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.
- elihu 7y agoI think some saunas can get to that temperature.
- fendy3002 7y agoWater vapor from boiled water seems much easier
- adventured 7y ago
- kposehn 7y agoIf 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.
- MithrilTuxedo 7y agoI'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.
- amluto 7y agoA 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.
- edoceo 7y agoI use the water method, who cares about the label? To keep honey from getting crystals just drink more tea.
- amluto 7y agoI 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 :)
- Waterluvian 7y agoThis might not be in good taste but this line of discussion is just hilarious to me.
- koolba 7y agoIs the resulting mask totally sterilized that it could be used without issue by a different person?
- Scoundreller 7y agoFrom 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.
- petilon 7y agoWouldn'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?
- Scoundreller 7y agoIt 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.
- fspeech 7y agoHow moist? They will contain moisture from any use.
- Scoundreller 7y agoTrue, 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.
- smacktoward 7y agoThe 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.
- mk6 7y agoIs there a method if an oven is not available? In a bag in a microwave?
- fspeech 7y agoThere is a metal clip on the respirator for fitting.
- bacon_waffle 7y agoNot 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.
- tiredwired 7y agoThe article mentions microwaves melting the masks.
- francescopnpn 7y agocheck the last article I submitted.
- jessriedel 7y agoMicrowaves work by heating the water in food. They don't work properly on paper. The dryer is a much better alternative.
- ravenstine 7y agoWeird 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.
- colechristensen 7y agoJust guessing that the static charge comes from a coating which is soluble in alcohol but not water.
- ancorevard 7y agoFYI. Dr. Larry Chu is an absolutely brilliant person. This should be considered as solid evidence and recommendation.
- maallooc 7y agoSterilize? Sure. But after it the mask won’t be able to filter on N95 level.
- Scoundreller 7y agoSlide 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.
- wideasleep1 7y agoWas 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...
- serf 7y ago>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.
- MivLives 7y agoWhat 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.
- ancorevard 7y agoOrigin https://aim.stanford.edu/covid-19-evidence-service/ https://aim.stanford.edu/covid-19-evidence-service/
- MivLives 7y agoFantastic! Thank you for linking this.
- wideasleep1 7y ago"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
- Scoundreller 7y agoIt 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.
- wideasleep1 7y agoSays 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.
- dheera 7y agoWhat about ozone? I've been thinking of putting them in a box and ozonating them.
- omar_a1 7y agoMy guess (only a guess) is ozone would work fine. It would probably be as effective as the UV treatment. And, again, all the caveats about ozone not being an empirically-evaluated sterilization method.
- metreo 7y agoHas this been checked on Snopes.com?
- nohat 7y agoHas no one tested putting it in a plastic bag and boiling it? At the very least they ought to explain why that's a bad idea if it is, because I can't be the only one to think that's the obvious solution.
- tartoran 7y agoThe temperature would be too high and would damage the microfibers
- WalterBright 7y agoI'm curious why UV light couldn't be used, or even X-ray machines, or one of those "gamma knife" machines.
- anonsubmit2671 7y agoThere was another study from 2011 showing the use of steam bags in microwaves, but localized extreme temperatures might destroy microfiber structures like putting microfiber cloths in a clothes dryer. 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/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3078131/
- saagarjha 7y agoTIL U+2103 DEGREE CELSIUS and U+2109 DEGREE FAHRENHEIT.
- dionian 7y agoif you're on a Mac, you can use alt-0 for a degrees symbol too
- saagarjha 7y agoThat's actually U+00BA MASCULINE ORDINAL INDICATOR. You want U+00B0 DEGREE SIGN, which is ⌥⇧8.
- doctorhandshake 7y agoUpvoted as one of the most HN comments I’ve ever seen.
- divbzero 7y agoI’m generally amused that a top thread for an N95 sterilization post is a Unicode discussion.
- malandrew 7y agoWhat’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?
- elihu 7y agoIt'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
- covercash 7y agoI 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?
- swader999 7y agoYes, 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.
- opendomain 7y agoI 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.
- coconut_crab 7y agoMy N95 mask smells like burnt plastic after 7 minutes under UVC (254 nm), I wonder if that means the mask is damaged.
- raleighm 7y agoFlagged this in hope of a more reliable source than a PDF in Box.
- wideasleep1 7y agoWell, apparently source Stanford App uses Box, link appeared in Reddit: https://stanfordmedicine.app.box.com/v/covid19-PPE-1-1 https://stanfordmedicine.app.box.com/v/covid19-PPE-1-1
- deleted 7y ago[deleted]
- bjoyx 7y agoThis was "fact checked" weeks ago as false (lol) https://factcheck.afp.com/novel-coronavirus-health-experts-warn-against-steaming-face-masks-reuse-after-misinformation-chinese https://factcheck.afp.com/novel-coronavirus-health-experts-w...
- Axsuul 7y agoHow is that the same? This is steaming
- ancorevard 7y agoThe fact check is obviously incorrect. But note that this research also considers "baking" in oven at 70 celsius for 30 min, and other tests.
- bjoyx 7y agoMy 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.
- rvnx 7y agoYeah the fact check is about steaming (which is totally unrelated and closer to autoclaving, which doesn't work)
- rfgasser 7y agoHow 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.
- remote_phone 7y agoE. coli are much heartier than viruses and harder to kill. If they kill bacteria they will definitely kill viruses.
- bufferoverflow 7y ago[citation needed]
- cmbailey 7y agoCitation 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/understanding-physiology-healthcare-pathogens-environmental-disinfection https://www.infectioncontroltoday.com/environmental-hygiene/...
- unwoundmouse 7y agoIt says in the article that (end of page 4) "4C Air confirmed all the proposed treatments have killed corona viruses."
- swader999 7y agoIf 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.
- mdani 7y agoWondering if direct sunlight would be as effective as UV light?
- robjan 7y agoThe ozone layer filters out most of the UVC light which is needed to destroy the virus / bacteria.
- charliewallace 7y agoAlternative method - how about putting the masks in a box with an ozone generator? Comments?
- swader999 7y agoDangerous and it degrades them.
- jaequery 7y agoanyone know the effects of spraying sanitizers all over the mask after use?
- robjan 7y agoIt's covered in the article. Sanitisers cause the mask to lose effectiveness due to loss of static charge in the microfibres.
- twomoretime 7y agoDoes 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.
- joppy 7y agoSurgical masks have an air gap, so are not comparable to N95 masks at all in that regard. They are solving different problems.
- shard 7y agoWhat 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.
- dcsommer 7y agoHere's a study on the surface lifetime of SARS-Cov-2: https://www.nejm.org/doi/10.1056/NEJMc2004973 https://www.nejm.org/doi/10.1056/NEJMc2004973
- ardy42 7y agoThat 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.
- alephnan 7y agoEvery 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 https://www.lg.com/us/styler-steam-closet It's relatively effective according to this article
- extralego 7y agoRich people
- Cantbekhan 7y agoThe dutch are doing it with hydrogen peroxide in their official recommendations https://www.rivm.nl/en/documenten/reuse-of-ffp2-masks https://www.rivm.nl/en/documenten/reuse-of-ffp2-masks
- ngcc_hk 7y agoIt 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.
- nsxwolf 7y agoIt'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.
- syspec 7y agoWill the rubber bands on them melt at that temperature
- aethertap 7y agoNo, I've done this with my mask (n95, same one I use for wood working) four times now and it appears to be fine.
- sizzle 7y agoAnyone 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-Particulate-Filter-2091-07000-AAD-P100-100-EA-Case/?N=5002385+3294780267&rt=rud https://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-...
- einpoklum 7y agoFrom 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!
- opendomain 7y agoI 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)?
- 10Meadowood 7y agoDoes anyone know if this applies to the N95 masks with a cool vent?
- woodchuck1 7y agoIt 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