Ideally, an N95, or similar respirator mask is designed to be worn only once. it should then be discarded. That’s a no brainer. And that’s what we did as health professionals pre COVID.
Now there’s a global shortage of masks, with such a shortage. hospitals around the world are looking for ways to be able to reuse these masks. they’re forced to find ways to decontaminate the masks and reuse them. We just can’t throw these masks away after one use like we used to.
So how can we decontaminate these masks and still keep them safe and working properly.
3m, one of the main us manufacturers of N95 has published a white paper. In which they list four criteria that must be met. In order to reuse their masks:
1, Inactivate SARS-COV-2, the virus that causes covid 19.
2, not damage the respirators filtration.
3, not affect the respirator fit.
4, be safe for the person wearing the respirator.
In other words, it can’t have any harmful off gassing as a result of the treatment. 3m is very clear and that they do not recommend reuse or decontamination of their masks. Stating that no method achieves all these goals. That being sad though, we’re in a pandemic and we have to make do
so what’s the best method of decontaminating our and 95? What if it’s our one and only N95, we have to reuse over and over and over again.
Well, let’s back up and take a few moments to talk about the construction of the mask itself. And N95 is made up of multiple layers of polypropylene nonwoven fabrics. When we were creating our filter masks, we actually dissected the 95 so we could see all the different layers.
Among these layers. The most critical one is the middle layer, which is produced by a melt-blown process. This layer is anywhere from 100 to 1000 microns in thickness. And it’s comprised of polypropylene micro fibers with a diameter in the range of one to 10 microns. You can see it in this electron microscope picture here of the melt-blown layer.
As you see, all these little teeny fibers are melt-blown in an arrangement. That looks a lot like pickup sticks. This arrangement creates a 3d network that has a porosity of 90%. This leads to very high air permeability. But because these fibers are so far apart, you may think there’ll be no filtration benefit, you may think harmful particles can just float through the fibers like water through a sieve
not so, these fibers get charged into quasi permanent dipoles called electric. So they get an electrostatic charge. Basically, once this layer is charged, it traps harmful particles. These fibers are electrostatically charged as they are created. This charge that they have allows the mask to filter much better. Without adding any density; Without making it more difficult to breathe through. If this is weakened or lost, the mask efficiency plummets.
So while the makers of n95 do not recommend reuse or sterilization of the respirator masks, we are critically short, all of these masks worldwide. We’ve got a compromise which is a whole different issue. We are really just trying to do the best we can do with what we have, which is kind of sad, but true.
The CDC has issued some guidance regarding a few methods of decontamination. The six most studied decontamination methods are as follows in no particular order:
3, 75% alcohol
4, household diluted chlorine bleach solution (Not recommend)
5, ultraviolet or UVC light
6, vaporized hydrogen peroxide gas
Some methods like vaporized hydrogen peroxide can only be done in hospitals. Or other large institutions that have access to the materials and the required equipment. Please guys, don’t try to make vaporized hydrogen peroxide at home it’s actually really dangerous and it can become explosive.
UVC light has its own hazards. It’s currently difficult to get a UBC machine and even if you get your hands on one disinfection parameters are very specific.
Other methods are just not good for you. They’re toxic, they’re flat out toxic, things like a diluted bleach solution, they’re not a good idea.
One solution will disinfect your Mac, it will also leave a residual toxic gas that you’ll be breathing in all day.
So that leaves alcohol, steam and dry heat.
After reviewing multiple studies, we feel that dry heat or heat with a very specific humidity is the best way to go.
Using dry heat will make the mask lasts longer. However, heat with a specific humidity is better at deactivating SARS COVID. Scientists looked at alcohol disinfection. So while treating was 70% ethanol has been shown to be 100% effective in inactivating the virus. The N95 mask integrity is impaired. The mask just doesn’t filter as efficiently and it never fits the same again. It doesn’t provide an adequate seal. There’s a protocol called the Italian protocol where the mask is sprayed with 70% ethanol, the front of the mask is sprayed 10 times. The mask is then flipped and sprayed an additional five times on the interior. This protocol did prove effective.
Currently, though 70% ethanol is very hard to find and thus the protocol is not practical for the average person.
So back to the protocol we suggest. It works well with little to no degradation of mask quality.
We can use this method to sanitize your mask upwards of 10 to 20 times.So here’s all the stuff you’re gonna need：
1, a Ziploc container, you want a 1.25 quart size container.
2, a convection oven, with no direct line of sight to any radiative heat sources. which would cause potential damage to the mask.
3, a paper towel
and 5, an eyedropper.
So here’s what you’re going to do.
First, you’re going to preheat your oven to 85 degrees Celsius, which is 185 degrees Fahrenheit.
Then, you’re going to place your mask inside the container face down.
You’re going to cut a 2.5 by 2.5 inch square of paper towel and place it in the container alongside the mask.
you’re going to drop 500 microliters, which is a half a milliliter or 10 drops of water onto the paper towel.
This will provide the mask with the exact amount of humidity needed, which is about 60%.
Then you’re going to place the lid on the container nice and tight. Place the container inside the pre heated convection oven. Again, that’s at 85 degrees Celsius or 185 degrees Fahrenheit. Next, you’re going to let it disinfect or cook for 30 minutes. Because it actually takes time though to get the mask up to temperature, the total time in the oven will need to be at least 40 to 50 minutes.
Then you’re going to take it out you’re going to open the lid and you’re going to rotate the lid 45 degrees. What this does is it allows air to naturally flow around the mask and dry it out. You only have to do that for five minutes.
After that you are done your mask is safe for reuse.
So there you have it what we feel is the safest and most effective way to disinfect your n 95 or homemade quality filter mask. stay healthy. Stay well!