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3M does not recommend attempts to sanitize, disinfect, or sterilize N95 masks [pdf] (apsf.org)
19 points by bookofjoe 42 days ago | hide | past | web | favorite | 24 comments

Of course they don't - there is no upside to tell people to do so. If it fails, 3M could be sued; if it works, 3M would lose sales.

That said, if you don't have any other mask, I fail to see how viral material can survive a soak in alcohol for a few minutes and then drying overnight in a warm spot away from flames (alcohol is flammable).

But see "Disposable N95 Masks Can Be Decontaminated, Researchers Confirm":


> We concluded that 75% alcohol solution and chlorine-based solutions were detrimental to the static charge in our meltblown fabric, and resulted in reduced efficiency. https://stanfordmedicine.app.box.com/v/covid19-PPE-1-2

How does ozone fare in eliminating the threat but not degrading the material?

I'd assume it would degrade N95 masks. Ozone reacts at least somewhat with both polyethylene and polypropylene at relatively low temperatures and short timelines. This paper shows effects at 95F and 15-90 minute exposures: https://sci-hub.tw/10.1163/156856195X01012

> "That said, if you don't have any other mask, I fail to see how viral material can survive a soak in alcohol for a few minutes and then drying overnight in a warm spot away from flames (alcohol is flammable)."

The linked NYT article points out "Of those methods, they did not recommend ethyl alcohol because although it killed the virus, it degraded the mask material."

"A second marriage is a triumph of hope over experience."—Samuel Johnson.

The Times article may represent a scientific example of Johnson's exemplar.

Or maybe they actually know what they are talking about and are just sharing their best information as responsible humans concerned with people doing stupid stuff during a pandemic in the name of saving a few bucks.

Is that the one that suggests baking at around 165 degrees Fahrenheit for 30+ minutes? Makes sense because that temperature will denature pathogens' proteins and nucleic acids, but won't damage the mask material.

If you have 3: wear them for shopping, go shopping just once a week, rotate the masks and store in dry non-sunny place

Someone had suggested microwaving - it doesn’t destroy static charge.

Wouldn't that be an issue for the metal nose clip?

From what I understand, metal is only a big problem when the metal is the only thing in the microwave.

For all the cynical comments here, 3M has published guidance on sanitizing and disinfecting half and full facepiece respirators:


Note that TCID and some other specialty treatment centers (TCID solely treats TB I believe) have been doing this for a while (although not necessarily with 3M masks).

Source: https://www.ncbi.nlm.nih.gov/books/NBK540078/

According to WebMD, COVID-19 can live up to 5 days on various materials (https://www.webmd.com/lung/how-long-covid-19-lives-on-surfac...). Why not just have a rotation of 6~7 masks where every mask that can be reused is left in a clean location for over 5 days so no sterilization is needed?

Does anyone know the source of that research, I am very surprised they are claiming 4 days on wood.

Results published earlier this month showed no detectable virus on wood after two days, and additionally found non-flat surfaces, like wood, to be more resistant. It seems unlikely that the virus will last 4 days on outdoor decking as WebMD claims.


A few weeks ago I heard this as one rationing system being used. If it didn't get any blood or other obvious contaminants on it they'd put it in a paper bag and date it, then wait 14 days (that was the recommendation at the time). I imagine they were reused by the same person, too.

FWIW some CPAP machines use ozone in their cleaning cycle. One might be able to jury-rig the CPAP to cycle ozone through the mask during that period.

HP does not recommend refilling ink cartridges. Coca Cola does not recommend reusing plastic water bottles with tap water.

Has anyone tried dry cleaning the masks? Its a pretty tough solvent and viruses are made partially of fatty acids.

PH, reducing agents, radiation, heat have been tried. Would adding pressure do anything?

I just hang it. Does that work?

No. It has two problems:

* COVID19 isn't the only threat. Other germs can multiply with time. This is not the time to go to a hospital with an infection.

* When I last looked, there was preliminary evidence COVID itself survives surprisingly long in a mask (I think days)

Okay so I'll hang it then. Brain overloading.

If you're taking an N95 out-of-rotation, you might as well follow best-practice: Dry heat. 30 minutes. 75-95C. They're a scarce resource.

It's annoying to see them going to people who don't use them right (a Republican senator was wearing one upside down). Incorrectly used, they're no better than a surgical mask.

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