From a physician in Orange County, CA:
“I personally have been microwaving my N95 mask at home everyday so I can reuse it since I travel to several clinics per day and see some high risk patients. The microwave denatures the proteins (and by extrapolation, the virus) and makes it safe to reuse! (the same procedure is used to clean our kitchen sponges)..”
Microwaves are used in medicine for disinfection of soft contact lenses, dental instruments, dentures, milk, and urinary catheters for intermittent self-catheterization925-931. However, microwaves must only be used with products that are compatible (e.g., do not melt) 931. Microwaves are radio-frequency waves, which are usually used at a frequency of 2450 MHz. The microwaves produce friction of water molecules in an alternating electrical field. The intermolecular friction derived from the vibrations generates heat and some authors believe that the effect of microwaves depends on the heat produced while others postulate a nonthermal lethal effect932-934. The initial reports showed microwaves to be an effective microbicide. The microwaves produced by a “home-type” microwave oven (2.45 GHz) completely inactivate bacterial cultures, mycobacteria, viruses, and G. stearothermophilus spores within 60 seconds to 5 minutes depending on the challenge organism933, 935-937. Another study confirmed these resuIts but also found that higher power microwaves in the presence of water may be needed for sterilization932. Complete destruction of Mycobacterium bovis was obtained with 4 minutes of microwave exposure (600W, 2450 MHz)937. The effectiveness of microwave ovens for different sterilization and disinfection purposes should be tested and demonstrated as test conditions affect the results (e.g., presence of water, microwave power). Sterilization of metal instruments can be accomplished but requires certain precautions.926. Of concern is that home-type microwave ovens may not have even distribution of microwave energy over the entire dry device (there may be hot and cold spots on solid medical devices); hence there may be areas that are not sterilized or disinfected. The use of microwave ovens to disinfect intermittent-use catheters also has been suggested. Researchers found that test bacteria (e.g., E. coli, Klebsiella pneumoniae, Candida albicans) were eliminated from red rubber catheters within 5 minutes 931. Microwaves used for sterilization of medical devices have not been FDA cleared.
Boomers Daily 
How long does this doctor microwave his face mask to kill coronavirus? Thanks.
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The doctor said she microwaves the mask on high for 30 seconds. Then lets it cool for 30 – 45 seconds. She microwaves it again for 30 seconds and lets it cool for 30 – 45 seconds. You can do it for 3 – 4 cycles. The key is to not burn the mask. 30 seconds seems to be just right, let it cool and repeat for 30 seconds.
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How is the doctor microwaving an n95 mask when they have a metal strip on the nosepiece so as to ensure a snug fit?
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As per earlier comment, if N95 has metal strip, microwave for 30 seconds, wait 30 to 45 seconds, microwave for 30 seconds, etc… Let the metal cool down. Best to repeat 4 – 5 times with cool down each time. One mask at a time only is what doctor stated.
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Thank you for an easy to understand answer to whether or not I can use my microwave to sterilize my N95 mask until I can obtain fresh ones.
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I’m not a medical professional, just a mom – but I still need to go out and get groceries and other essentials. I’ve taken to making a fabric cover mask to go outside my n95 mask ( as I only have 1 and I need to make do). I wash the fabric cover after each use. Not sure how long before my n95 mask will be done for but, I don’t want to buy other masks and be part of the problem either. For me this is the balance between limiting my exposure and still being a good citizen.
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There are several studies out there that have been published, specifically on microwaving N95 masks to kill pathogens. The results show that microwaving, while killing a virus, will also MELT the interior parts of the respirator filter making it, unbeknown to the user, ineffective. Read some studies, Google search will find them, published in medical journals.
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I wonder if a “spritzer” water spray on the mask might increase the temperature and be a bit more effective.
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Most of the studies of using microwaves to treat viruses on a mask point out that steam, not the microwaves, kill the virus. How this is done I will have to read more, but I would think that placing a small dish of water below the mask will help. See the following: Heimbuch, B.K., et al., A pandemic influenza preparedness study: use of energetic methods to decontaminate filtering facepiece respirators contaminated with H1N1 aerosols and droplets. American Journal of Infection Control, 2011. 39(1): p. e1-e9.
Fisher, E.M., J.L. Williams, and R.E. Shaffer, Evaluation of microwave steam bags for the decontamination of filtering facepiece respirators. PLoS One, 2011. 6(4).
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If the virus has water or any other polar molecules in it, the microwaves will cause self heating without needing supplementary water to generate steam. Google “dielectric heating” for detailed explanation. Wiki also explains it well. The primary mechanism for dielectric heating is “dipole rotation” If the material being microwaved has any ionic content, there is further heating by radio waves due to ionic drag. The single strand positive (rotation sense) RNA inside of the 120nm (avg diameter) lipid shell of the coronavirus is reported to have polar molecular components. Sugar phosphates. Sugars are usually thought to be weak polar moment (electrically) so idk the degree of heating possible. idk if the “lipid bilayer”shell itself has any moleculular components that are polar. The lipid tails between the layers contain coding that determines the temperature at which the lipid melts. But most fats that have a polar moment are weak so there is a question regarding how effective microwave heating will be.
https://en.wikipedia.org/wiki/Lipid_bilayer
The spikes on the outside of COVID-19 that are partly composed of proteins. idk if they are polarized. idk if the RNA is supported in a liquid inside the shell and if that liquid has polar molecular structure.
Note however that it will be rare find a single pristine dry COVID virus floating around or stuck to a mask fiber. it is more likely stuck to a partially dried glop of spit/snot/sputum that will initially have some water in it and will steam the virus if subjected to microwaves.
Some work needs to be done to itemize every component of Covid-19 and quantify the polar moments of the bits that it is made out of to have more confidence in the (polar rotation) self heating mechanism of each part.
There are however a number of papers that show success microwaving viruses. 7 minutes is one of the longer microwave oven run times I have seen reported to 100% disable a large collection of viruses. further reading:
https://www.sciencedirect.com/science/article/abs/pii/003042208590355X?via=ihub&fbclid=IwAR1DxCa9rY73TCkUQmPYF2KZYoRvkdz-NZ3eY2sVofXi6e48OHSZT2z8f6g
https://www.ncbi.nlm.nih.gov/pubmed/3884686
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Check my comment – Naxbie
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I read someone sprayed their mask with saline solution then nuked for 2 minutes . I did the same but just sprayed with water, both sides , making sure it covered the whole mask as I assume the water would heat up and kill any virus. The mask is totally dry when removed.
But my microwave oven went capt.
That makes sense as one is not supposed to turn on an empty oven, and the mask is not enough substance. I should have put a mug of water in the oven with the mask.
Got a new oven and that is what I’ll do from now on.
I would not bother with the saline as I think that would leave a salt residue.
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