You’re not supposed to reuse the common N95 filtering facepiece respirator mask. But given that they’re almost impossible to find (or impossible to afford) amid the coronavirus pandemic, here are some acceptable methods to decontaminate and reuse common N95 masks.
We’ve gathered advice from three credible sources:
- N95 guidelines for healthcare professionals from the CDC
- A 2009 paper in the Annals of Occupational Hygiene
- An article by Dr. Peter Tsai, a designer of the modern N95 mask
First, how not to clean your N95 mask
To maintain the effectiveness of the mask, never use these methods:
- Spraying or wetting with aerosol or liquid alcohol.
- Washing in soapy water.
Dr. Tsai indicates that these methods can break down the inherent electrostatic charge that is key to the way an N95 filters small particles. They can reduce a mask’s effectiveness by a third to a half.
How to clean your N95 mask?
There are three cleaning methods, which experts find credible and you can do easily at home.
Method 1: Rotation
Dr. Tsai cites a study in the New England Journal of Medicine that uses a round robin rotation of masks so that each one is rested for at least 72 hours before being worn again. Tsai has not experimentally verified this method himself, but it relies on the widely held belief that the coronavirus should not survive more than 72 hours on an inhospitable host, like the surface of an N95 mask. The downside to this method is that you need four masks per wearer, and that’s assuming you use only a single mask each day. But if you just make a single trip for essentials any given day, the numbers work.
Method 2: Steaming or boiling
Dr. Tsai says submerging an N95 in 125C/260F degree steam or boiling water for 3 minutes will disinfect the mask without significantly reducing its filtration efficiency (FE). Don’t excessively stir the mask if you boil it, use only enough manipulation to keep it submerged. If your mask has paper outer and inner layers, neither the steam or boiling methods are advisable as they will disintegrate those paper layers that hold the filter medium between them.
Method 3: Baking
I hesitate to include this method because, while simple, it assumes you have a second, dedicated oven for this purpose. If not, you run the risk of contaminating your main food preparation oven. Researchers at Michigan State University refined this method using a laboratory oven, and Dr. Tsai concurs that heating a mask for 30 minutes at 70C (160F) is an effective decontamination method.
The most important step
Don’t ruin your freshly decontaminated mask by handling it incorrectly. Don’t let your hands create a bridge between the particle-trapping front of the mask and the ostensibly clean back of it. Practice these CDC N95 steps to don and doff your mask properly.
Never throw your use masks to the river or sea.
While the CDC officially says there is no way to determine the number of times you can reuse a mask safely, these techniques from credible viral transmission experts create reasonable alternatives in this unprecedented time.
It is unfortunate that no articles on the subject of masks ever notes that some people have N95 masks because they where paying attention to what was happening and purchased them before ANYONE was talking about a shortage. People like myself have a couple dozen masks. I only wear one once a week when I go to the grocery store . I am shopping for my wife and me as well as my 88 year old parents. I deliver the groceries with a mask on. I have a reason to be careful. It is unfortunate that articles such as this make well prepared people out to be guilty for having a few N95 masks. My masks where ordered on Jan. 20. I sterilize them with special germicidal UVC lamps so they can be reused (same as some hospitals are doing). And to just push the point a bit further – I also have a few dozen P100 mask which I purchased back in 2009 during the H1N1 flu epidemic. N100 and P100 mask filters are like HEPA filters which are nearly 100% effective with particles down to 0.3 microns. I don’t feel guilty for having these either.
This is post. I´ve been thinking of starting a site on this topic myself.
Best regards,
Boswell Valenzuela
I expect the filter media (generally a non-woven fabric) to be degraded. Basically, you’re trying to oxidize the pathogen, but other materials exposed to the ozone will be affected. We’ve got an ozone generator we use to remove smoke and mold odors from books, but also inside musty motor vehicles. One hour in a closed vehicle is enough to make rubber bands brittle and easily breakable. So, the effect on the filter material may be similar, reducing its filtration effectiveness. You could try it and see if there is ay detectable change in the pressure required for inhalation and exhalation. If the needed pressure changes that could indicate the material is “clogging” (possibly from small pieces that have disintegrated) or (the reverse) been removed so filtration is reduced. The wiggle here is that the test sensitivity (your subjective breathing experience) may not be sensitive enough to detect changes in airflow. Multiple ozone exposures over time may be eve more difficult to detect because your comparing with the very last time you used the filter, not its initial condition. I hope that makes sense.
But if its a choice between the ozone and nothing . . .
Still, if you’ve got a microwave oven the wet steam in a bag method has some testing behind it.
Someone said they use of vaporized hydrogen peroxide to disinfect N95 masks:
It is reported as an effective disinfectant method. Perhaps hospitals without the units specifically designed for this disinfecting method could jury-rig one as follows:
– Place a benchtop isolation chamber in a hood.
– Place a cool mist ultrasonic humidifier filled with…
I currently use a SoClean machine that uses ozone to clean my mask. Based on what I have read, Ozone has been proven to kill the SARs Coronavirus. I have bought a second machine and modified it slightly so it is a completely closed unit that bathes the contents in Ozone for 7 minutes. The unit makes you wait about two hours for the ozone to be changed back to oxygen before opening the cleaner. I run the mask through two cleaning cycles.
Based on what I have read, a study is going to be published that shows Ozone kills the COVID-19 virus. Why don’t the hospitals build ozone chambers to decontaminated the masks after use. Ozone generators are very cheap.