
Ask HN: Irradiation to reuse surgical masks? - vermorel
High-quality surgical masks require nonwoven fabric that appears to be in short supply at WW level. Reusing masks is typically a big no-no due to obvious reasons. Autoclaving them is not an option either as it would damage the fabric. However, what about reusing the (somewhat) extensive food irradiation facilities to reuse masks faster? Viruses are notoriously resistant to the usual kGy doses used for food, but my (uneducated) guess is that it&#x27;s a matter of dosage, RNA is a complex fragile molecule. Is there any blocking element that would prevent mask reuse after suitable irradiation?
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viggity
I bought a few UV-C lamps for this very purpose. I'm sorry I can't find the
research I found, but it said that UVC does indeed work, but lowers the
efficacy such that it's not worth it more than 5 times (although, I think'd
rather re-use a UVC N-95 mask than make one out of paper towels or a home sewn
one).

The same research said isopropyl alcohol was a terrible idea as it kills the
electrostatic nature of the filter. It said a light bleach solution worked
best and could be re-used indefinitely.

A DIFFERENT study showed that soaking in a saltwater solution (NaCl) and
letting it dry was extremely effective. As droplets hit the micro salt
crystals the a very small solution forms, then recrystalizes as it dries. The
crystalization essentially rips the virus apart.
[https://www.businessinsider.com/mask-coated-in-salt-
neutrali...](https://www.businessinsider.com/mask-coated-in-salt-neutralizes-
viruses-like-coronavirus-2020-2)

There are some anti-viral masks that use citric acid, AFAICT for the same
reason. bulk Citric acid can be bought in the canning aisle at any grocery
store as it is needed to make jams. Although I imagine salt is even easier to
find

[http://ryanpharmacy.com/curad-antiviral-face-
mask/](http://ryanpharmacy.com/curad-antiviral-face-mask/)

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saurik
The studies show you can UV-C them (it reduces the physical strength of the
mask but not the filtration ability, and can be done many many cycles: I think
I saw at least 20); have you actually tried searching for how to sterilize
masks yet?

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wuunderbar
Can you provide said studies?

~~~
chuckledog
Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator
Filtration Performance and Structural Integrity,
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699414/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699414/)

NYTimes.com: As Coronavirus Looms, Mask Shortage Gives Rise to Startling
Solution, [https://nyti.ms/3b8C1HQ](https://nyti.ms/3b8C1HQ)

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sloaken
Great idea, I love it. Only reason I can think of is fear of lawsuit. "they
reused a mask and I caught xyzzy" \- of course there is no proof that was the
source, but nuisance lawsuits are common.

~~~
pacamara619
You seem to be forgetting that the rest of the world is not as litigious as
people from the United States.

~~~
Gustomaximus
Add to that the emergency nature of the choice is reuse or have nothing. I
suspect lawsuit risk at least today is limited.

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anewvillager
Here's a Nebraskan protocol for reuse of disposable masks

[https://www.nebraskamed.com/sites/default/files/documents/co...](https://www.nebraskamed.com/sites/default/files/documents/covid-19/COVID-
Extended-Use-Reuse-of-PPE-and-N95.pdf?date=03182020)

~~~
shirazi
protocols.io is manually entering all protocols related to COVID-19 on the
platform for free and this would be a good fit for it. There are protocols for
making your own hand sanitizer and things, in addition to coronavirus research
protocols.

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burfog
Autoclaving is fine. Pick the hottest non-damaging temperature.

The plan in some places is to put a mask in a paper bag, write the date on it,
and leave it in a warm place for two weeks. This does require that every
worker have two weeks worth of masks, plus spares to replace masks that get
really splattered.

~~~
vermorel
Not sure about that. Electrostatic properties of the nonwoven fabric must be
preserved. Tough pathogen likes spores must be eradicated as well. Then, the
"warm place" must be kept sterile, or it's going to become the infection
vector. The solution must be scalable.

~~~
burfog
Coronaviruses do not make spores. Even new masks are not sterile. Paper bag
storage scales with the number of employees; each employee needs personal
space for 14 small paper bags such as lunch bags.

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vermorel
Hi All, long story short, it is possible, and limited trials have just been
started in France with specialized actors. More details (in French)
[https://blog.vermorel.com/journal/2020/3/23/sterilisation-
de...](https://blog.vermorel.com/journal/2020/3/23/sterilisation-des-masques-
par-rayonnement-ionisant.html)

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Gibbon1
I don't know what the answer is but it's a materials problem. Almost all
medical stuff gets sterilized after manufacturing and packaging. The common
ways are gamma radiation, ETO gas, steam. Less common are ebeam and Chlorine
Dioxide.

There is no golden process. Materials especially polymers have limits to how
many times they can be sterilized. Different materials/different processes.

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rubidium
What about just letting it sit out in the sun for a couple days? Sunlight and
warmth kills the virus. Would it have a negative material effect?

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vermorel
Covid-19 isn't the only pathogen around, there are many tougher pathogens. I
suspect a few days of sunlight won't be enough for those.

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toomuchtodo
Are there any gamma emitting devices at hospitals that could repurposed for
this? Such as those used for cancer therapy? Or imaging devices (CT scanners)?

~~~
vermorel
I doubt it. Those devices are not designed to pour lots of kGy into stuff.
Food irradiation typically involve some kind of lead-covered mini-tunnel with
the radioactive source in the middle. Definitively not an expert, but I
suspect the radioactive sources used for food irradiation to be two to four
orders of magnitude stronger than what is used for therapy.

~~~
yummypaint
Dosage for food is like a 1000 Gy, for therapy on people its more like 1-10. A
medical 60Co source could still reproduce the same effect by putting the masks
right against the aperture and increasing exposure time. No idea if this would
destroy viruses, though.

~~~
vermorel
I have found literature on this, look for "Sterways Process". It seems that it
starts to be safe virus-wise somewhere around 35kGy.

