As the COVID-19 pandemic nears its possible apex in New York State, the need for N95 respirator masks, which protect against inhalation of airborne coronavirus molecular particles, is still a top concern. According to new research being conducted at the Stony Brook University MART building, dry heat ovens have been shown to be effective for disinfecting N95 masks.
Led by Kenneth R. Shroyer, MD, PhD, Marvin Kuschner Professor and Chair of the Department of Pathology at the Renaissance School of Medicine, and a team that includes Glen Itzkowitz, Associate Dean for Research Facilities & Operations, and graduate students Sruthi Babu and John Yuen, the researchers conducted pilot studies to determine if N95 masks were degraded after multiple rounds of dry heat treatment.
Through the studies, they found that particularly 3M N95 masks passed quantitative “fit-tests,” the industry standard to ensure protection against coronavirus inhalation after multiple rounds of dry heat treatment. The heat treatment caused no visible structural damage and had no effect on the straps required to ensure proper fit, the study showed.
“Fit-test scores were virtually identical between masks processed through four repeated cycles, suggesting that this approach could effectively increase the usable supply of N95 masks by a factor of five,” said Dr. Shroyer. “It appears that the heat treatment can also be used to treat other types of surgical face masks.”
This study was completed in a high-capacity oven that could process thousands of masks per day, concluded the team. Yet, they said, “equivalent results could be achieved at most hospitals, clinics or nursing homes following a similar protocol in any conventional dry heat oven or incubator.”
About the Protocol
Healthcare providers place a used 3M respirator mask in a paper bag labeled with their name and work location before delivery to the processing center. The bags containing the masks are then sealed with heat indicator tape before they are placed in the oven. Following treatment for 30 minutes at 100˚C (212˚F), the same bags can then be returned to the clinical care providers.
Dr. Shroyer and colleagues concluded that heat treatment of N95 masks could be used at healthcare facilities that have no other viable options. It could provide a better alternative approach, recently recommended by the CDC, that both the general public and healthcare providers should utilize bandanas or scarves once supplies of face masks are depleted. Additionally, dry heat disinfection may be more readily available during the pandemic than hydrogen peroxide vapor generators. Although, according to Itzkowitz, a combination of vapor decontamination and dry heat decontamination would make for the best results.
“The team has discussed potential fabrication efforts to construct a sterilizer racking system capable of recycling as many as 8,000 masks a day through the heat treatment,” said Itzkowitz. “As many as eight institutions have already indicated that they may start using this technique for PPE recycling following COVID-19 exposure.”
PI Statement: Glen Itzkowitz Discusses What Led to the New Approach
I came into the project after autoclaving sanitization was attempted and determined to be a nonstarter. This had followed an email discussion about vaporized hydrogen peroxide solution the night before. We believe the autoclave failed due to the fact that when that equipment pulled vacuum and then heated up, the 1860 model masks would become deformed.
Think of an autoclave as a big pressure cooker. These masks failed fit testing by Environmental Health & Safety (EH&S). Ken [co-PI Dr. Ken Shroyer] and I were talking about this, and I told him about the dry heat sterilizer technology we installed in the MART DLAR satellite facility cage wash on MART level 3. This technology was selected over a bulk autoclave because of steam pressure limitations in that part of the MART.
Dry heat sterilizers are not pressurized vessels; they do not use vacuum as part of their process. We agreed to give this equipment a shot. The satellite vivarium (a place, such as a laboratory, where live animals or plants are kept under conditions simulating their natural environment, as for research) in the MART is not yet active so the equipment in this cage wash facility other than being installed at this time, had not been used yet. Ken’s team determined soak cycles and tested a variety of PPE at different temperatures as well as lengths of cycles, temperature set point deviations, and ramp down time cycles.
The initial testing on the 1860 model was at 250˚F (121˚C) for a duration of 60 minutes with a 30-minute ramp down and a 5˚C deviation. These masks failed the qualitative fit test by EH&S following this soak. We then decided that temps were likely higher than they needed to be and cycles were too long. The next attempt used the 1870 model N95’s at 250˚F for 60 minutes. These masks passed. (The 1870 model is a soft frame N95, it is the less commonly used mask in healthcare compared to the 1860 rigid frame model.)
We started a discussion with the equipment manufacturer, TPS Gruenberg, and asked them what they knew of similar studies and efforts. They offered to come to our site to spike thermal data collection probes into the masks and retest. We ran another test on five 1870 masks with the engineer from TPS and got some very interesting data. It is also interesting to note that a bacterial biological thermal indicator was placed into the masks run in this test by Ken’s lab. The bio indicators were all color changed following the soak at 250˚F. This indicates a positive 6 log kill (a log reduction or “kill” means the amount, by percentage, of biological material is 10 times smaller than a given starting point. Therefore, 6 log means that 99.9999% of the biological material is killed). 6 log is needed to claim disinfection.
Because the TPS Gruenberg equipment works by convection heat with a HEPA filtered exhaust, there is a natural cooler location in the chamber itself. Hence, this part of the chamber will take longer to heat up to the desired set point. Having located the “cool” corner of the chamber through the test we ran on sight with the TPS engineer, we made some really informed decisions for retesting the 1860 model.
We knew we were onto something when TPS asked us to speak on a conference call they were organizing about using this platform for PPE recycling following COVID-19 exposure. There were about eight other institutions on that call.
Following that, Ken and I reviewed the previous cycles and determined the appropriate recipe for sterilization. We layered that over what we learned from analyzing TPS’ data logger test. The result was the following change to the protocol:
- Cut the duration of the cycle soak time because we understood where the chamber was more efficient.
- Test in places in the chamber where the heat gradient is more uniform.
- Reduce the set point temperature to 100˚C and achieve a 6 log kill of the virus (COVID-19) on the mask based on other coronavirus literature that Ken has been reviewing.
- Use a sealed lighter weight paper autoclave bag because the temperature was now lower than previous tests.
- Secure the bag to the rack frame so that they would not be moved out of place by the convection fan internal to the equipment. Thereby attempting to keep all things uniform during the testing.
- We also discussed fabrication efforts to construct a truck (sterilizer racking system) that would be capable of heating approximately 1,000 N95’s per 30-minute cycle. Hence in an eight-hour day recycling as many as 8,000 masks.
One other consideration that we had discussed: our equipment is HEPA (High Efficiently Particulate Air) Filter equipped. This is very important in a convection heat sterilizer. It ensures that if any aerosolized virus particles escape, the sealed autoclave bags are filter trapped during soak and killed as the filter heats up as well.
Please contact state health officials with these findings, so that the information can passed on to nursing homes where PPE is scarce.
Good point. Will follow up on that. We already sent a summary to the CDC.
Questioning whether this process could be used with a regular convection oven without HEPA filtration as a means to reuse N95 respirators during the COVID 19 pandemic. Can you offer recommendations? Thank you.
Thanks for the questions. Our testing was performed in a controlled environment. Our equipment is HEPA filtered. HEPA filtration provides an added measure of containment for particles that can aerosolize during convection heating.
I think that a regular oven should be OK if preheated but agree that a convection oven could be a problem.
We are looking at the possibilty of using our combi-ovens to sanitize the PPE at the hospitals.
Almost every restaurant/hospital/large serving kitchen in World has one…
This is ours:
I looked at the technology on the link you included. Is the system exhausted via a HEPA filter? Our test utilized a HEPA filtered convection heat sterilizer at lower temperatures. Among the benefits of the HEPA filter is that any virus that might become aerosolized during the disinfection cycle will be trapped. The filter face will conduct sufficient heat, we believe, to thermally destroy the virus that would be trapped in the matrix of the filter.
The coronavirus pandemic has infected 1.7 million people and killed more than 103,000. The country now has more than half a million cases. New York state alone has more cases than any other country in the world.
Use a mask if you didn’t get one yet here is where my son got for all our family. I saw someone here was looking for it.
? N95 masks https://bit.ly/3ebXmm4
Thank you so much, Amanda, for sharing the link. I’ve been looking locally for weeks now and couldn’t find it. So happy that I will have them delivered to me for free.
I got 50 for me and my family and 50 for the donation. Stay safe
Appreciate that Amanda. Just received my pack of 20. Great quality, it came in 2 days and it’s free. Thanks a lot
Mine was delivered yesterday. It is a great deal, and I don’t have to go out and get infected while I am looking where to buy. Thank you.
The grocery chain makes coronavirus face coverings mandatory for customers, so you can’t get in without it. All must wear a mask. It might stay like this until next year.
Until we get a vaccine, which is a while off, this is going to be our new normal, and we need to adapt and protect ourselves. In two days we have now 2 million cases with more than 130,000 deaths.
Received mine too. Thank you, Amanda! Facemasks must be worn correctly, changed frequently, removed properly, disposed of safely and used in combination with good universal hygiene behaviour in order for them to be effective. I recommend it to everyone.
would you trust a mask that has no manufacturer label? no.
I received my order too. Excellent quality.They have the label and packaging.
I got it too. They are great quality.Just reordered another 100. Thank you.
The CDC recommends wearing a cloth face mask in public to help slow the spread of coronavirus. I ordered another 100 today.
Those are KN95 korean N95 not the same thing and nothing like the picture. I have some and they fall apart.
Those are not n95 masks, I followed the link. Be careful.
What about non- convection oven?
Can households use this dry low heating method with success?
Also what about household pressure cookers with hydrogen peroxide?
Hi Bill- Our test was performed in a controlled environment. Lower temperatures are the key to mask integrity, however they must be in range to thermally destroy this virus as well. Convection heat is efficient heating, but in our case was backed stopped by HEPA Filtration. We did not test a conventional heat system. Let me know if you have any additional questions. Glen
I agree that a non-convection oven should be OK if preheated. Important, however to not overheat since masks were fine at 100C but were damaged at 120C.
Be cautious about using ovens with exposed heating elements. The air temperature might only be 70-100C, but the filter material strongly absorbs the infrared radiation. This allows the surface to get much hotter, which will quickly damage the masks as Dr. Shroyer states. If your oven has exposed elements, consider wrapping the mask in parchment paper or tenting it in foil like you would poultry. Make sure the air can still convect in, but that the heating elements don’t have line-of-sight to the mask.
Bill- one more thing. I would be very cautious about using Hydrogen Peroxide in a pressure cooker. Glen
can a pressure cooker with hydrogen peroxide solution 3% be used at home for reuse of n95 or surgical masks?
Thanks and regards
Please don’t use pressure cookers like this. They are not intended to be used this way. At a minimum the integrity of the mask will be compromised. I also don’t honestly believe this is a safe use of a pressure cooker. Glen
Please elaborate on the type of bag that was used during this process. Was it a typical sterilization pouch. For example, was it one side paper/one side plastic with internal indicators as we use in dentistry.
Hi Linda- our initial tests at higher temps required the use of heavier craft paper style autoclave bags. Sort of like a very heavy weight paper bag. We started to reduce temperature we were able to begin using lighter weight bags. Paper burns at 233C. Our soak temperatures were never that high. It’s a great questions. Glen
where can i purchase this dry heat sterilizer for surgical mask and N95 .
We used a large medical grade oven that is capable of processing about 1000 masks/cycle. Any routine non-convection oven, however, would probably work fine provided that it can maintain a steady temp of 100C but not go above that temp.
Can heating in a home oven sterilize handmade cotton masks
What temp and time do you recommend ?
thank you !
Should be fine but we only tested surgical masks.
Wouldn’t ironing a homemade cotton mask sterilize it? I believe irons generally heat to 3oo degrees fahrenheit.
my dental office has a dry COX sterilizer for sterilizing surgical instruments. Would it be the same? I can vary the time and temperature.
I think that the Cox sterilizer uses a combination of dry heat and pressure. We know that N95s are damaged by autoclaving but we did not test dry heat under pressure.
How big are these units?
How much for the unit?
Would this lend itself to a counter top in a dental office?
How many 3M models did you test. I use the 8511 with the respirator valve. Did you test that model?
Did you look at filtration efficacy after treatment?
How is this compared to microwave assuming no metal parts in the mask?
We used a TPS Gruenberg bulk lab animal science sterilizer ” that can treat about 1000 masks at a time. This company makes a number of smaller units, including some which I understand are about the size of an under-counter refrigerator. I don’t have pricing info.
we only tested 3M model 1860 and 1870 masks.
We tested filtration efficiency after treatment and all heat treat masks had quantitative fit test scores that were indistinguishable from the control (untreated) masks.
We did not test microwave treatment but I’ve seen some online sites that don’t recommend it.
I don’t think the convection or fan is necessary as long as the heat is applied long enough. Thus a plain dry hear sterilizer can be used for smaller offices. The lack of a fan will prevent the spread of the virus.
Or just a heated rice cooker with a wire rack without any water as was shown by the Taiwan Prime Minister. Most small offices don’t need to do more than one to three masks at a time.
Makes sense to me so long as the temp does not exceed 100C.
How will small dental offices be able to do this? We are the #1 most dangerous profession. Especially because of aerosols which are emitted with treatment.
No doubt! The methods described, however, could be performed in a wide range of ovens.
Does microwave work? was it tested?
Please see above. Not tested.
In the studies I have read, they state that 133 degrees is required to destroy the virus. Why is only 100 degrees being used? How do you know if the virus has been destroyed?
I think you may be referring to Fahrenheit rather than Celsius. Prior studies show that other coronaviruses in culture media are disinfected at much lower temperature (75C). We have not attempted to culture virus after dry heat treatment at 100C because this could only be performed in a special (BSL3) facility.
the outer coat fatty acid melts at 69.6C, inner coat protein capsid melts at 87C, nucleic acid core genome RNA (the brain of the virus) melts at 91C, although the virus escaped when it sensed temperature of 68C, I hope it has no place to hide inside the hot oven
As a general dental practitioner with a 4 chair surgery, would this process also work if the masks are paced in sterilisable bags and placed in a home oven at 100 degrees Celsius for 30 mins? It is becoming a real challenge to source FFP3 masks so any advice welcome with regards to reusing these.
I think this would work so long as you don’t exceed 100C.
Use a wireless thermometer, put it inside/into the bag without the probe touching any heavily heat conductive materials, and keep a close eye on the actual temperature inside. Home kitchen ovens have a very large temerature error margin and slow reacting thermostats. So expect to have to adjust temperature and open/close the oven door a little bit, until you get a handle on how to keep your specific oven, close to a steady 100 celsius.
Does this mean that an ordinary conventional or convection oven can be used at a temp of 250F for 30 minus.?
250C is too hot and will damage the mask. We found, however that masks were not damages at 212C. I don’t recommend using a convection oven unless it’s equipped with a HEPA filter.
at water boiling temperature of 215F in the oven, my mask rubber band after using it 4 times, it breaks
[…] single use masks, according to new research being conducted at the Stony Brook University MART building, dry heat ovens have been shown to be effective for disinfecting N95 masks. […]
DO NOT USE A MICROWAVE
Please comment on the idea of putting a mask in a microwave for some time period, and the resultant effect one could anticipate in cleansing the mask
To do so would require removal of the metal nose band and straps that are attached with staples. This would likely damage the mask. While I have not tested microwave treatment, I don’t think it should be be done.
How to make it simple? A very well renown virologist told me the SARS cov2 virus disintegrates above 50 degrees celsius. So she recommends to put ordinary paper face masks into the ordinary home stove at 60 degrees celcius for 10 minutes to maintain their protective protection
Published studies showed that a closely related virus, SARS-CoV-1 requires heating to 75C, in viral media. It’s very possible that dry heat will take longer or higher temperatures to be effective so we focused on treating at 100C.
Can one also use a regular oven that does not have convection. Please test this as convection ovens are not as common.
This should work equally well in a conventional oven that has been preheated to 100C (212F). It should not be done in a convection oven unless the blower is equipped with a HEPA filter.
What about putting the mask inside a seal bag and let it in a tumble dryer for about 1 hour at 70C?
Needs to hit 100C
According to this article https://www.ncbi.nlm.nih.gov/pubmed/14631830 also 60min at 67C are enough… (or 90min at 56C and 30min at 75C)
There are many pest control companies across the country that have heat trailers to kill bed bugs. One of these could easily be set-up in a parking lot and could be used to sterilize numerous masks or surgical gowns. Heating equipment can also be placed in a room, and some exterminators also have portable, free-standing heat chambers. Remote heat sensors are typically used to verify that the correct temperature is maintained.
That’s thinking outside the box! Seems like a great idea if they can hit and hold the target temp and either don’t have an exhaust fan or if they do, are protected with a HEPA filter. I’d be worried though about whether the temperature is uniform throughout or if there are relative hot and cold spots inside.
That’s what we have been trying to tell govt, hospitals etc., but no reply. We have been heat treating for 10 years. It’s already proven to kill Ebola, norwalkvirus, Coronavirus (not the current strain) but we can’t get anyone to listen. Bcbedbugexpert.com
So you do not need a HEPA filter if your dry – heat sterilizer does not have a fan. Is this corrrect? Thanks
I’m not in your field but know a little about practical problems– For nursing home use, wonder if inexpensive food dehydrator could be used such as https://www.amazon.com/COSORI-Dehydrator-Stainless-Temperature-Compliant/dp/B07PY5M579 Would need to resolve protocol to address possible contamination to larger area since heating unit is by design not closed
Looks like that might work but Id be worried if it has a blower that could aerosolize virus before the incubator hits sterilizing temperatures.
Is UV exposure another alternative to disinfecting N95 masks? And if so how long.
I understand that has been used and could work. Have not tried it, however, myself.
Please tell lay people how to best sterilize their masks at home we don’t have autoclaves.
Info on how to sterilize the best we can with what is available in a typical home; oven, microwave.
I understand that it won’t have the efficacy of a medical facility.
Advise on temperature, length of time and if it’s possible to use hydrogen peroxide to add the steam.
Please advise. Most of us are lucky to have a few, but we’re MUST reuse.
I have not tried this in a home oven but expect that it should work and I would use it myself if I had no other options.
My best guess (this has not been experimentally validated):
1. Preheat your regular kitchen oven (not a convection oven) to 121F.
2. Place you N95 mask on the rack and cook for 30 min.
3. Turn the oven off and allow it to cool for 30 min before removing the mask.
Be careful to not exceed 121F by more than a few degrees, since going to 250F can degrade the function of the mask even though it might look OK. I don’t know at what point between 121 and 250F, this becomes a problem. If you are not sure about the accuracy y of your oven, it would be a good idea to do a trial run using a thermometer. This assumes, however that your thermometer is accurate.
Hi Kenneth – not sure if you will see this reply. I do not think that 121F is a high enough temperature to kill the virus, and might leave you with a false sense of security (though I agree that you shouldn’t heat it too high or it could harm the mask). Here is an article mentioning that some strains of Sars-CoV-2 can survive at temperatures up to 140F (60C) for an hour. https://www.newsweek.com/coronavirus-heat-kill-virus-1498074 . I’m not sure the exact temperature, but it’s worth doing some research. Here is an article summarizing a scientific study examining different techniques to sanitize n95 masks; the researchers heated their masks to 185F for 20 minutes in the study and found it effective. I hope this is helpful to someone. https://www.sciencedaily.com/releases/2020/05/200505164638.htm
To add to my previous comment – I have see variations in temperature used in these sanitizing protocols. Someone in this comment thread even mentioned testing a method of heating them at 65C (149F), saying that this lower temperature would help preserve the structural integrity of the mask. I do not know the optimal temperature; however, I think 121F is too low. I only wanted to say that it’s worth doing some digging about the best temperature to use, if you’re going to try this. Good luck to you all.
We have tried running our N95s in our Getinge washer with only a dry cycle. 170′ F for 60mins, has anyone else tried this?
Is this function for all types of N95 masks? Is a specific process to be followed? Is this recognized by the CDC and OSHA? And of course manufacturer. Thank you.
We only tested 3M N95 masks. I understand from a physician in Italy that N95 masks used in Europe might be damaged at 100C. I have also not tested KN95 masks (made in China).
PS: We have reported this method to the NY State DoH and to the CDC but have not yet received a response.
What about doing this at home — is a standard convection oven dry enough to achieve dry heat sterilization using the protocols above?
Does not need to be a convection oven and if the blower is running before the oven hits 100C, it’s possible that this could blow virus out of the oven unless the oven has a HEPA filter. I think that a better option to try is a regular (non-convection) oven, preheated to 100C.
Do you know what a convection oven is? It does not need a Hepa filter. It creates a uniform temperature in the oven by gently circulating the air in the oven. It does not use exterior air.
My oven’s lowest temperature is 110 C (230 F) so I left a surgical mask in there for 15 minutes? How effective would this be?
I have not tested masks at 110C. I know, however that filtration capacity is degraded by treatment at 121C for 30 min.
Can I use my microwave to clean my kn95 mask? What temperature if I can use the microwave?
We have not tested KN95 masks. Also, I don’t know if microwave heating will degrade the filtration properties of a mask.
KN95 masks may be just as effective as N95 masks, although I understand that they are manufactured for use in China.
If your has a metal nose strap, it much be removed before you put it in a microwave and its likely that will damage the mask.
Sir how many times can be made this proccess ??
We successfully heat soaked 1860 masks for four 30 cycles at 100C.
Would using a hair dryer be effective to disinfect the mask?
I am not sure how you would uniformly manage temperature using a dryer. Secondly, whatever is on the surface of the mask would be scattered likely in an uncontrollable way because of the force of the fan in a hair dyer.
Not a doctor, but he mentions above there are concerns about blowing the virus around so I would say no to hairdryer.
We are testing dry heat with 30 minutes at 65 +- 5 °C, since the virus should be killed by 65 °C for 10 minutes.
Each mask is closed into a polyopropylene sealed container to avoid cross contamination within the oven.
Moreover, keeping this low temperature allows a better reuse of masks without altering their filtering capabilites.
We do believe that dry heat is the right way to decontaminate masks from viruses.
We have tested relative humidity inside the boxes. It icreases for first 10 – 12 minutes after the beginning of heating, and then falls.
Did they only test kill for COVID19? What about other microbes of concern that are usually not killed at 100 degrees Celsius for 30 minutes of dry heat? Are they just disinfected or sterilized?
We have not tested kill for COVID-19. The target was selected based on a prior published report that treatment at 75C for 30 min will disinfect COVID-19 in culture media. We selected a higher temp that did not impact the ability of the mask to filter 300 nm particles, the industry standard of N95 mask performance, recognizing that dry heat could be less effective than wet heat at the same temperature. We hope to test COVID-19 kill in our BSL3 lab, once our cultures are ready to test. We have no plans to test disinfection of other more heat-stable microbiologic agents; this is focused only on ways to kill COVID-19.
I am building large ovens in shipping containers for a solution now, we using multiple solutions to kill COVID including heat. I sent you an email please let me know if we can help in any way, I would love a chance to discuss.
Hi Ken, I respect all your efforts in allowing HCP to be able to decontaminate without the fear that the virus is still present. You and your collegue have given great peace of mind to one’s looking for some semblance of protocol to proceed with. I see currently the CDC is not on board with Dry Heat sterilizers. Do you know why? I am a general dentist and was planning on using a FDA approved Wayne 500 Dry Heat Sterilizer to decontaminate. I can get six respirators per load in their own paper bag. My oven takes about ten minutes to get up to temp. It seems that as we move into this next phase of transition, especially for DDS’s who are at high risk, it only make sense to use an apparatus that is readily available in our profession. The top three listed through the governing body are impractical and economically unfeasible. I would be pleased if you responded with your thoughts.
Do you keep the heat on the full 30 minutes
Already figured this out by reading studies on temperature and the virus. I now disinfect from COVID-19 in my oven at 150° for 60 minutes.
In a warm/hot day (75F+ degrees ), I parked my car under the sun, put the mask inside a paper bag, then put them on my car dashboard with all windows closed. To check how high the temperature went inside the bag, I poked an oven thermometer into the bag. The temperature inside the bag reached 160 F within 10 minutes! This is why you must NEVER ever leave your kids/pets/plants inside the car!!!!
I think this method works for masks used by people who are not health care professionals tending patients or essential workers who face many people and have to put mask on all day. Correct me if I am wrong.
I am an endodontist and do not have access to an oven with a HEPA filter. We have an industrial strength toaster oven. Would that be acceptable, or are we subject to viral vapor? Thanks
My dds is suggesting staff place there used N95 mask in a paper bag and store in a certain place for 3 days. After we then can reuse it again. Per the dds this process kills the virus? Is this true? And we are suppose to get 10 uses out the same mask doing this process.
Can I use a commercial garment steamer to sanitize my N95 mask? I read moist heat was preferable. If so, how long is enough? It gets very hot.
I am curious why you did not try to use the autoclave at rest. We have Steris autoclaves that sit between 180-210 inside the chamber while it isn’t even running. We have tested it with thermometers. Open the door put the masks inside. Shut the door set a digital timer. Timer goes off open the door and take the mask out. similar study was done by Stanford by Amy Price, DPhil (Oxon) and Larry Chu, MD. They also discussed making sure the masks were suspended and not laying on or near metal to protect the electrostatic property of the mask.
Can you describe the protocol for testing for viral activity? Are you measuring activity within the mask or infectivity of air passed through the mask? Does the presence of active virus within the mask show that air drawn through the mask is infective? My guess is that after heating there may be quite a high within-mask threshhold before the air is contaminated.
I have a dental office with a clinical staff of 3 people. Do you see any reason why 3M
N-95 masks, which are so scarce, could not be heated in a toaster oven at 212 degrees Fahrenheit? I was thinking of maybe placing them on some aluminum foil in the middle of the oven. If I am nuts, please don’t laugh. I am just trying to make the N-95’s I have last until the supply increase. Thank you.
1) Does the dry heat affect the electrostatic charge, and if so, to what degree?
2) Does the dry heat process affect the vent on front-vented N95’s?
I leave my mask on my dash. Car in the sun all day. Altitude 4500ft. Cant hurt!!
Might a citizen with a convection oven be able to put their oven on 215 proof in a parchment bag & appreciate similar effects? We have a washer, but no dryer. Our masks contain a small heavy nylon & wire “stiff” fit at the nose. We have no clothes dryer
[…] https://news.stonybrook.edu/sb_medicine/dry-heat-ovens-can-effectively-disinfect-n95-masks/ […]
[…] not made to be reusable can be placed in the oven at 158 degrees Fahrenheit for 30 minutes. Even 212 degrees Fahrenheit has been tested with minimal damage to N95 masks. If an oven is used, it is wise to place the masks […]
I place my masks in the direct sunlight all day. Then I put in a reg oven for 15 min at 180F I have zero leaks and I work in a high risk area.
I hope in first part it has been cleaned The sunlight is UV light which is itself will work for your purpose
[…] N95 masks in your home oven and these will work brilliantly for our cardboard products too. This study successfully showed viruses dying at 212 degrees for 30 minutes, and other studies have even showed […]
Iam doing the mask sanitization in following ways at home after reading thru various links and studies ……comparing dry heat,moist heat- steaming, vapo.hydro-perox,UVC radia, alcohol, bleach etc.
I bought a dedicated digital electric oven with convection air flow- keep 75 deg celsius x 60mins, check static charge, put each sterilized into sandwich plastic envelopes and store it..use it again and repeat same x 20 cycles then throw it. (no moisture in a dry heat oven, higher temp >100c reduces mask effi% and airflow resistance)
The static charge remains good x 20 cycles of heat treatment also ( bring the mask cone near ur arm or chest( body hair) or hanging nylon/polyester cloth- see it moves), careful to hold mask by its strap after sanitization.
After reading this ariticle, thinking to scale up to 100 deg C x 30mins x 10 cycles and discard… dr glen , your advise will solve this catch22 situa.
Check our project here: https://create.arduino.cc/projecthub/needlab/face-masks-disinfection-device-needlab-3ed2f5
Portable Dry Heat mask sterilization equipment. I am the the US Distributor for AMB Ecosteryl in Belgium. They have recently developed a portable / cost effective mask sterilization unit called the M-Steryl. I have attached a link to the specs of the unit here.
I can be reached at email@example.com for questions or anyone interested in purchasing. These units sterilize up to 2000 masks per day and are the size of a college dorm fridge and plug into a regular outlet.
Can this dry heat method be used in a regular, non-convection oven at home? I f so at what temperature and for how long to sterilize a 3M 8210 Plus N-95 mask?
Could you do the same to clean a KN95 mask?
I know that N95 masks with valves are a no-no. BUT if I’m closed to running out of the
N95 w/o valves, I use a valved one with a surgical mask over it.
Question: can I put an N95 -VALVED mask into a rice cooker for one hour at 100C w/o the heat melting the valve?
Your article will surely help many people, thanks for sharing!
Covid-19 is a disaster for the whole world, may all come through it safely
[…] Convection ovens aren’t just for cooking anymore – they’re also being tested to disinfect masks! Seriously, what can’t these ovens […]
Why can you not use sunlight withvtheir infrared rays to sterilize thr 3M n95
I left my K95 mask in the oven. It melted within in a few minutes. Now I am afraid to open my stove considering it may have the virus in it, and the melted plastic is most likely not good for my lungs. Thanks.
[…] For additional details about the initial studies that served as the foundation for this study—which was launched during the first wave of the pandemic in April 2020—see this story. […]
[…] For additional details about the initial studies that served as the foundation for this study—which was launched during the first wave of the pandemic in April 2020—see this story. […]
[…] For additional details about the initial studies that served as the foundation for this study–which was launched during the first wave of the pandemic in April 2020–see this story. […]
Has anyone considered washing the masks with soap? or dish or clothes detergent? and maybe drying either in the air or having the masks each in net bags and in the clothes dryer?
Home use of sterilization without fancy equipment can be helpful for families.
[…] early study by the Department of Pathology at Stony Brook University experimented with dry-heat ovens and N95 […]
Why did you not look at an even lower temperature point such as 70 deg C and then seek to find the key duration / dwell time to achieve log 6?
This could save time and costs – plenty of papers appearing suggesting 100 deg C is not the key temperature for sterilisation and a lower temperature could result in less structural damage to the masks.
1. This work is two years old now – have you followed up? Is there a link?
2. The “fit” test is the standard, but the flow test is crucial – by which I mean, how many 0.3-micron particles get through the mask at normal breathing differential pressures? Did you run this test? (non-trivial)
2.5 My ongoing concern has been that heating the polypropylene would change its electrostatic properties, and I know of no reason to believe (orfor that matter disbelieve) that the polypro automatically regains those properties on cooling – obviously this affects the particle-trapping efficiency. Any thoughts?
Many thanks, both for the work and for the anticipated reply