
Electric cooker an easy, efficient way to sanitize N95 masks, study finds - johnny313
https://news.illinois.edu/view/6367/143865832
======
Jerry2
My family has been decontaminating our N95 masks with ozone. I bought a
battery-operated O3 generator and if you place it into a tupperware container
along with the mask, it will decontaminate it and then you can use it the next
day. Yale School of Medicine has done a study on the efficacy of this method.
[1]

I prefer this method because it doesn't degrade the mask at all, it needs no
disinfecting/harsh chemicals, it penetrates into the pores of the mask
completely, and it's near fool-proof.

[1]
[https://www.medrxiv.org/content/10.1101/2020.05.28.20097402v...](https://www.medrxiv.org/content/10.1101/2020.05.28.20097402v1)

~~~
rayuela
Wow this is actually incredible if this works. However this study was tested
bacteria and relate it to covid in the following way:

"an ozone application achieves a high level of disinfection against PsA, a
vegetative bacteria that the CDC identifies as more difficult to kill than
medium sized viruses such as SARS-CoV-2 (Covid-19)"

Would the implication be that this same method works on covid as well? That is
not immediately apparent to me...

~~~
solinent
It sounds like it's saying "ozone kills the tougher bacteria than Covid at a
very high rate".

So directly it says absolutely nothing about Covid but implicitly it does seem
to state that it should also kill Covid since it's less tough to kill than the
vegetative bacteria. I guess they can't make that statement directly--there's
no evidence related to Covid here. I'd ignore it.

~~~
im3w1l
But why are they making this proxy argument, why not test with covid directly?
Makes me think they did test with covid and it wasn't working.

~~~
solinent
Maybe the mechanism of death is similar so if it kills a more difficult strain
the same mechanism will kill the "easier strain". It doesn't directly state it
though, I think it's just speculation. It doesn't belong in a science paper
except maybe in a speculative section about the future I guess.

------
asperous
The main thing is consistency, as ovens/cookers are temperature controlled.
Other bootleg options are available:

Household clothes driers can get hot enough as well, but not all of them do.

Cars on a hot day can also get to the desired 140-150f+ range.

Many dishwasher sanitize cycles as well

[https://www.who.int/csr/sars/survival_2003_05_04/en/](https://www.who.int/csr/sars/survival_2003_05_04/en/)

[https://dailyhomesafety.com/does-dryer-kill-bacteria-and-
ger...](https://dailyhomesafety.com/does-dryer-kill-bacteria-and-germs/)

[https://heatkills.org/how-hot/](https://heatkills.org/how-hot/)

[https://www.quora.com/What-temperature-ballpark-does-the-
hea...](https://www.quora.com/What-temperature-ballpark-does-the-heated-dry-
function-of-a-dishwasher-operate-at)

~~~
Wowfunhappy
Question is whether the oven / dryer / dishwasher damages the mask's filter.

------
foobiekr
Related: can anyone explain why there are still no n95 masks available? It
seems like, a few months in, it's surprising that there are none available for
non-medical buyers.

Is this perception wrong?

~~~
noelsusman
They're not widely available to non-medical buyers because they're still not
easily attainable for medical buyers. N95s aren't the easiest thing to
manufacturer, so ramping up production to fully satisfy current demand would
require a significant investment in time and capital. Companies aren't going
to do that without some certainty that they'll actually be able to sell enough
of their extra production to cover the initial investment. Nobody has provided
them that certainty, so they haven't made the investment. Instead they're
(mostly) just maxing out production on whatever equipment they already have.

I work for a hospital and have been heavily involved in our COVID-related
supply chain efforts. Six months into this we are still struggling to find a
reliable source of high quality N95s. Our standard suppliers are getting us
100-200 per day, but we're using 10 times that every day.

~~~
pushswap
My company tried donating 120 boxes of 3M N95 masks to our major local
hospitals at the beginning of the pandemic. We only asked that the expense
would not be charged to patients directly or indirectly. None of the hospitals
accepted the masks based on the no indirect billing part.

~~~
quicklime
I can see why they would refuse to do this. The effort of tracking which masks
were donated vs which to charge for, would be significant.

Who’s going to track which patient was treated by staff wearing donated masks,
and which were not?

And if medical staff were working with multiple patients while wearing the
same mask, would they have to split the discount for a $1 mask up between
patients?

~~~
pushswap
We just wanted our donation to be a donation to patients and staff, not to the
business side bottomline. Since n95 masks are practically fungible, it could
have easily been credited or treated as a donation to patient bills (as we
suggested) whether it be to divide among X random Covid patients or to a
single person's ICU bill. The masks value was around $25,000, and who knows
what multiple (3-25x ?) the hospital would charge to patients?

The fact is the hospitals gave us no path toward transferring that to patients
and not their bottom line. We ended up selling most of our masks to hospitals
for that reason, seeing it as the more moral option.

------
everybodyknows
SARS Cov-2 infectiousness decays exponentially, with the time constant a
function of temperature and humidity. A two-parameter calculator:

[https://www.dhs.gov/science-and-technology/sars-
calculator](https://www.dhs.gov/science-and-technology/sars-calculator)

~~~
distances
Would it be wrong to infer from this that letting a face mask sit in room
temperature for a week is almost guaranteed to make it safe for use again?

~~~
radus
Not wrong at all. I do 3 days in paper bags. Reasoning for paper is that it
breathes more than plastic and the half life of the virus is shorter on paper
as well.

------
avivo
Don't just look at single studies. This is a meta-review resource:
[https://www.n95decon.org/implementation](https://www.n95decon.org/implementation)

It's a collaboration among the many people doing research on decontamination
that also takes into account the tacit implementation knowledge of those who
conducted the studies.

~~~
everybodyknows
Thanks -- within that review we have this link:

[https://www.n95decon.org/files/heat-humidity-technical-
repor...](https://www.n95decon.org/files/heat-humidity-technical-report)

There's a table of mask damage as a function of high temperature exposure
time. All tests were well below the 100C cited by OP.

------
kevin_thibedeau
Many N95s are rated for a month (20 days) of 8 hours use. If you're only using
them for a few hours a day you can stretch their life by quite a bit.

~~~
akiselev
That's what I've been doing with a pack of N100s and it works fine. The
problem is threefold: leaving it in a car out in the sun will quickly melt the
glue holding the plastic filter to the mask, after a few uses it just quickly
gets contaminated on the inside unless you're obsessive about decontamination
before taking the mask off each time, and that month rating is because the
plastic fibers used to make the electrostatic filter dry out and crumble,
which can also be pretty bad for your lungs.

~~~
bitL
Why don't you cycle 3-4 of them, wearing a different one each day? Viruses
won't survive for longer than 3 days inside, so cycling multiple masks would
solve the possible contamination issue.

~~~
jradd
what conditions are present to make this a constant? just heat and oxygen?
moisture?

~~~
sgc
70F / 21C and 50% RH or something close to that, is how standard "indoor"
environmental conditions are tested in general.

------
Abishek_Muthian
I wonder whether the results change with the pressure cooker.

I had ilizarov apparatus[1] on my legs for over a year(once during age 7 and
another during age 15) and my mom used to sterilise the instruments (Scissors,
Forceps) used for dressing wounds at home(every alternate day) in pressure
cooker(on advice of the doctor).

I presume, pressure cookers are still being used for the sterilisation of
instruments[2] in several parts of the world as its still common than an
electric cooker.

[1][https://en.wikipedia.org/wiki/Ilizarov_apparatus](https://en.wikipedia.org/wiki/Ilizarov_apparatus)

[2][https://cdn.ymaws.com/sites/adint.site-
ym.com/resource/resmg...](https://cdn.ymaws.com/sites/adint.site-
ym.com/resource/resmgr/NewsArticles/Use_of_pressure_cookers_for_.pdf)

~~~
necovek
I am sure they perform sterilization effectively, but introduction of
water/steam (which is under pressure in a "pressure" cooker) will almost
certainly deform a mask like an N95 mask.

~~~
Abishek_Muthian
I thought electric cooker uses less water in contrast to no water.

~~~
necovek
My reading of the OP was that no water was to be used, and a towel is placed
at the bottom to shield the mask from touching the heating element altogether.

------
Xcelerate
I have a set of N99 masks that I just rotate over a period of about a week in
brown paper bags.

If you don’t have enough masks for that, I imagine a sous vide machine (like
the Joule) would work. Just seal the mask in a plastic bag and place under
water for the appropriate amount of time. These things hold very precise
temperatures.

~~~
mariushn
> I just rotate over a period of about a week in brown paper bags.

Why the brown paper bags? Do these ensure better evaporation?

Wouldn't simply keeping the mask somewhere kill the virus in 3-4 days? Or,
what would be the best way to ensure this within 3-4 days without any damage
to the mask?

~~~
radus
Paper bags are cheap, provide adequate containment, allow moisture to
evaporate, and the virus is stable on paper for less time than on plastic.

~~~
Xcelerate
Mainly this. And I can write the date of last use on the outside of the bag.

------
RobLach
Wouldn’t that jeopardize the filtration ability of these masks by affecting
the fields of the electrets under heat?

~~~
weaksauce
absolutely. don't do this please. The filter is able to filter out particles
smaller than 0.3um by using weak electrostatic forces. baking it will make the
mask less effective. if you can just have a few masks that you rotate
through... the best would be a 3 day rotation.

there's a good reason the CDC doesn't say to do this.

anyway .3 micron particles are the hardest for a mask to filter out because
they are small and tend to go in a straight line more than the smaller
particles. the filtration effectiveness of the mask is a u shaped curve with a
trough in the region of the .3 micron particle sizes.

------
pydry
I bought one of these UV sanitizer boxes to sanitize my N95s:
[https://www.amazon.co.uk/gp/product/B085XZPLVS/ref=ppx_yo_dt...](https://www.amazon.co.uk/gp/product/B085XZPLVS/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1)

I'm still not totally certain how well it really works, but I know it works
better than those UV wands (you need at least a few minutes of exposure).

It's also neat for a few other things that it's probably healthy to sterilize
a bit more frequently (e.g. keys, phone, toothbrush heads).

~~~
hbcondo714
Yup, my wife went all out and got one of those UV sanitizer boxes[1] too along
with the Under Armour face masks[2]. Their instructions say to wash it but
it's convenient to just place in a box. We have also been cleaning other items
in there including baby toys.

[1] [https://lumolite.com/](https://lumolite.com/)

[2] [https://www.underarmour.com/en-us/p/ua-
sportsmask/1368010.ht...](https://www.underarmour.com/en-us/p/ua-
sportsmask/1368010.html)

~~~
Johnny555
I can understand how UV light can sterilize hard surfaces like a cell phone,
but how does it sterilize multi-layer fabrics where the virus may be shaded
from the UV light by the fabric?

~~~
Wistar
And that is called the shadow effect. The UV-C doesn't much make it into the
plastic statically-charged inner layer of the mask.

In May I built a 5-ft long 24x24" cross-section sealed plywood box with a
small (6x6") MERV13 filtered inlet opening and an auto-detailing fogger filled
with 3% hydrogen peroxide at one end. A center chamber with a web of small
hooks on a wire frame for the N95 masks, mirror (plexiglass) glued on the
walls of the center chamber to bounce the UV-C around and an 18" long Blade
UV-C (254nm) lamp that peers in through a slot on the top of the chamber. On
the far end I used a ~30cfm duct fan to pull the the hydrogen peroxide fog
through the chamber and masks and a flexible duct to take the exhaust outside
my garage. I used UV-C dosimeter disks to tune the amount of time needed for
proper UV-C exposure (about 5 mins or so). I put the masks in it, turn on the
Blade UV-C lamp, turn on the fogger and let it go for about an hour. I then
turn off the fogger and let the fan pull fresh air through for another hour or
so. It's not pretty but I think it is effective.

My wife thinks I am crazy.

------
cf100clunk
An autoclave is what the electrical cooker is being used to emulate. A
pressure cooker is a better option if you'll be on the road, camping, or
otherwise without electricity. Researchers in Canada already proved several
months ago that N95 masks could be sanitized this way:

[https://news.ycombinator.com/item?id=22761264](https://news.ycombinator.com/item?id=22761264)

~~~
westurner
Unfortunately the referenced NewsArticle does not link to the ScholarlyArticle
[https://schema.org/ScholarlyArticle](https://schema.org/ScholarlyArticle) :

"N95 Mask Decontamination using Standard Hospital Sterilization Technologies"
(2020-04)
[https://www.medrxiv.org/content/10.1101/2020.04.05.20049346v...](https://www.medrxiv.org/content/10.1101/2020.04.05.20049346v2)
:

> _We sought to test the ability of 4 different decontamination methods
> including autoclave treatment, ethylene oxide gassing, ionized hydrogen
> peroxide fogging and vaporized hydrogen peroxide exposure to decontaminate 4
> different N95 masks of experimental contamination with SARS-CoV-2 or
> vesicular stomatitis virus as a surrogate. In addition, we sought to
> determine whether masks would tolerate repeated cycles of decontamination
> while maintaining structural and functional integrity. We found that one
> cycle of treatment with all modalities was effective in decontamination and
> was associated with no structural or functional deterioration. Vaporized
> hydrogen peroxide treatment was tolerated to at least 5 cycles by masks.
> Most notably, standard autoclave treatment was associated with no loss of
> structural or functional integrity to a minimum of 10 cycles for the 3
> pleated mask models. The molded N95 mask however tolerated only 1 cycle.
> This last finding may be of particular use to institutions globally due to
> the virtually universal accessibility of autoclaves in health care
> settings._

The ScholarlyArticle referenced by and linked to by the OP NewsArticle is "Dry
Heat as a Decontamination Method for N95 Respirator Reuse" (2020-07)
[https://pubs.acs.org/doi/full/10.1021/acs.estlett.0c00534](https://pubs.acs.org/doi/full/10.1021/acs.estlett.0c00534)
. Said article does not reference "N95 Mask Decontamination using Standard
Hospital Sterilization Technologies" DOI: 10.1101/2020.04.05.20049346v2 . We
would do well to record that (article A, seemsToConfirm, Article B) as third-
party linked data ( _only if_ both articles do specifically test the efficacy
of the given sterilization method with the COVID-19 coronavirus)

------
jaclaz
I don't want to appear a naysayer, but everyone should be aware that N95 masks
usually aren't effective at the intended level because of the lack of a fit
test and training by the non-professional users.

See:

[https://news.ycombinator.com/item?id=23957506](https://news.ycombinator.com/item?id=23957506)

------
petra
Generally,the instant pot requires at least 1 cup of water when running,
according to the manual.

How does this work without water ?

~~~
masklinn
I'm also wondering, IIRC rice cookers rely on the temperature of the pot not
exceeding 100C until all the water has evaporated (which is why getting the
correct rice/water amount is important). Without any water in the container I
would expect the pot to quickly exceed 100C and shut off.

Mine certainly seems to provide no way to maintain such a temperature, I'd
guess it'd just switch to "keep warm" and AFAIK that's nowhere near 100C
(maybe 60~70).

~~~
weaksauce
the cheap rice cookers use a temperature switch that triggers after it reaches
a bit over 100C yes.

~~~
masklinn
What do more expensive cookers use? A timer sounds more simplistic than a
temperature sensor, are they mixing the temperature information with something
else?

~~~
weaksauce
they use some more advanced logic than just on or off until it boils off the
water

[https://lifehacker.com/why-some-rice-cookers-are-20-and-
othe...](https://lifehacker.com/why-some-rice-cookers-are-20-and-others-
are-200-1783235798)

------
jefftk
How does this compare to just letting the mask sit for several days?

~~~
Falloodude
Cooking the mask ensures that microorganisms on it will die and not pose a
risk to the wearer. A mask sitting around for several days can still harbor
them in some cases.

~~~
jefftk
I see that in general, but if we're wearing N95s specifically to protect
against the coronavirus then several days seems like it should be (a) enough
and (b) not as hard on the mask?

~~~
coding123
This is what I do. I just place it in a plastic bag and don't use it for about
a week. I have enough to let me use one each day and quarantine the used mask
for a week.

~~~
mypalmike
What's the plastic bag for? Seems like a good way to promote bacterial and
fungal growth.

~~~
distances
I'm using open plastic bags for avoiding touching the mask itself. I figure
there's enough air circulation when I let the bag sit open on a shelf. Granted
a paper bag could be better.

------
aaron-santos
Happened to have bought a towel warmer with UV sanitation pre-pandemic. There
are some early reports that heat and UV neutralize the virus.

------
argonaut
None of this is necessary for non-healthcare workers, since the virus will die
off on a fabric mask in a few hours.

1) Not a single study has demonstrated that viable Sars-Cov-2 virus survives
on porous materials in the real world

2) Even before Covid, it was known for decades (common medical knowledge) that
human coronaviruses and flu viruses do not remain viable on porous materials
for more than several hours.

That this common knowledge is not so common knowledge among the public is a
failure of public health communication. The one or two alarmist studies
showing that the virus "survives" X number of days don't reflect the real
world because 1) the researchers literally directly douse or soak the surface
with a huge viral load, and 2) the researchers usually only look for viral
genetic material, not whether the virus can infect cells. Viability !=
detecting viral genetic material (same story for people - we shed viral
genetic material long after we stop being contagious).

There is a reason the CDC has always said surface transmission is rare:
[https://www.nytimes.com/2020/05/22/health/cdc-coronavirus-
to...](https://www.nytimes.com/2020/05/22/health/cdc-coronavirus-touching-
surfaces.html;) there have been no documented cases of surface transmission:
[https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-
si...](https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-
sick/cleaning-disinfection.html) Fortunately some in the media are catching on
to the hygiene (security) theater:
[https://www.theatlantic.com/ideas/archive/2020/07/scourge-
hy...](https://www.theatlantic.com/ideas/archive/2020/07/scourge-hygiene-
theater/614599/)

Citations for 1) and 2):

Most studies use unrealistic starting doses:
[https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099...](https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099\(20\)30561-2.pdf)

Other human coronaviruses don't survive long on porous surfaces (gone by 6
hours):
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134510/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134510/).
A hospital randomly collected patient and real surface swabs (including non-
porous surfaces) for original SARS, a minority were PCR positive, none of the
swabs were infectious (viral culture):
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134510/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134510/).
Same story for flu (virus can be detected for days, but inactive and not
viable after a few hours):
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3222642/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3222642/).

I could only find this study on Sars-Cov-2 that cultured the virus (still used
a huge viral dose in a lab setting, not the real world). Even though they were
able to culture the virus, only 1% of virus remains after 6 hours on a
surgical mask, several orders of magnitude less for cotton clothing:
[https://www.medrxiv.org/content/10.1101/2020.05.07.20094805v...](https://www.medrxiv.org/content/10.1101/2020.05.07.20094805v1.full.pdf)

This long post was originally meant to be a reply to someone asking for a
citation; it's yet another example of how much effort is required to combat
misinformation.

~~~
westurner
"Interim Recommendations for U.S. Households with Suspected or Confirmed
Coronavirus Disease 2019 (COVID-19)"
[https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-
si...](https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-
sick/cleaning-disinfection.html) :

> _On the other hand, transmission of novel coronavirus to persons from
> surfaces contaminated with the virus has not been documented. Recent studies
> indicate that people who are infected but do not have symptoms likely also
> play a role in the spread of COVID-19. Transmission of coronavirus occurs
> much more commonly through respiratory droplets than through objects and
> surfaces, like doorknobs, countertops, keyboards, toys, etc. Current
> evidence suggests that SARS-CoV-2 may remain viable for hours to days on
> surfaces made from a variety of materials. Cleaning of visibly dirty
> surfaces followed by disinfection is a best practice measure for prevention
> of COVID-19 and other viral respiratory illnesses in households and
> community settings_

------
exabrial
My big concern is modifying the electrostatic properties of the fibers which
is how much larger fibers stop much smaller particles (order of 10x-100x). It
looks like moderate heat and no humidity in this study didn't have those
effects. Hoping this can be peer reviewed soon!

------
matt-attack
Can someone explain why you can’t just have three masks, and circulate through
them? We’ve been told that the virus dies after 3 days just sitting there. Why
do I need to decontaminate it ad in TFA? I don’t get it.

~~~
jasonjayr
There are other things other than SARS-CoV-2 that can get trapped in those
masks that ought to be decontaminated by some means.

~~~
distances
Such as? Anything I wouldn't be inhaling in normal circumstances anyway?

------
anotheryou
I rotate 10 masks, wear each of them 20m/day at most. Drop out of rotation if
smelly (only happened once with serious sweating).

------
ablekh
I would not use this method for N95 masks with plastic exhalation valves due
to potential melting of the latter.

------
ConcernedCoder
direct sunlight kills everything eventually

------
romseb
Another way to clean masks is to put them in a bowl of hot water (at least
70°C) and add detergent. Let it sit for a few minutes and you‘re good to go.

~~~
snissn
this will damage n95 masks

------
clairity
if your concern is corona, there's no need to do any of this for most people,
most of the time (i.e., not a front-line worker). the likelihood of getting
live corona on the mask is pretty low, and any corona that does get on the
mask will die naturally overnight. certain situations like going to a party
might warrant it, but in that case, just throw the mask away and use a new one
next time.

if you're more worried about other bacteria and viruses, it's a little more
relevant, but not much for most of us. despite the endless news coverage, it's
just not worth worrying about unless you're often in elevated risk situations,
like being a medical worker. just wash your hands occasionally (particularly
after situations like going to the bathroom or handling raw meat).

~~~
BoiledCabbage
And the reasons people ask for citations is what you are saying is very
misleading. The CDC estimates that 45% of US Adults fall into these increased
risk categories. So no, it's not just people fighting off cancer it's almost
half the country.

> We estimated that 45.4% of US adults are at increased risk for complications
> from coronavirus disease because of cardiovascular disease, diabetes,
> respiratory disease, hypertension, or cancer. Rates increased by age, from
> 19.8% for persons 18–29 years of age to 80.7% for persons >80 years of age,
> and varied by state, race/ethnicity, health insurance status, and
> employment.

1\.
[https://wwwnc.cdc.gov/eid/article/26/8/20-0679_article](https://wwwnc.cdc.gov/eid/article/26/8/20-0679_article)

~~~
andai
Am I reading this right, does this mean that _45%_ of the country has a
serious pre-existing medical condition?

~~~
erichurkman
> A greater percent of men (47%) have high blood pressure than women (43%)

[https://www.cdc.gov/bloodpressure/facts.htm](https://www.cdc.gov/bloodpressure/facts.htm)

------
yingw787
I've heard you can use 151-proof grain alcohol in lieu of rubbing alcohol
(which has disappeared entirely from store shelves for months) in order to
sanitize things. Apparently if you mix it with vegetable glycerin you can
create your own ersatz hand sanitizer?

I was thinking you could create your own rubbing alcohol by mixing water,
sugar, and yeast, distill it over your stove, and then combine it with aloe
vera to create hand sanitizer, but that's probably less preferable than using
store-bought ingredients that are more consistent.

~~~
akiselev
Please don't disinfect an N95 or N100 mask with alcohol (of any sort). It will
dissolve the plastic fibers of the filter.

~~~
wrycoder
How do you know this?

~~~
klyrs
[https://smartairfilters.com/en/blog/sanitizing-masks-with-
al...](https://smartairfilters.com/en/blog/sanitizing-masks-with-alcohol-
degrades/)

~~~
wrycoder
Thanks very much for that link (and the links contained in it.)

I'm using 75% ethanol in a spray to "sterilize" (for SARS2 only, it's a
fragile virus).

Even if the efficiency drops after spraying (which is not the same as
soaking), I think it's still better than just a cloth or surgical mask.

The link to making high efficiency masks

[https://groups.oist.jp/nnp/diy-face-mask](https://groups.oist.jp/nnp/diy-
face-mask)

in the link you provided is quite interesting. The concept of HV electrostatic
blowing of polyethylene is new to me - I wondered how N95 masks were made. I
note that in the cotton candy machine experiments they reduced the voltage to
50V, lol.

I'm going to reserve judgement on the physics behind making electrostatically
charged fibers and the question of how long they retain the charge. That's an
interesting area to investigate! For example:

[https://www.tandfonline.com/doi/abs/10.1080/00022470.1974.10...](https://www.tandfonline.com/doi/abs/10.1080/00022470.1974.10470030)

Ethanol and isopropyl alcohol don't dissolve polypropylene, so the efficiency
loss must be due to some other effect.

If the small fibers in the N95 mask have charge embedded in manufacturing,
i.e. they are electrets, perhaps the removal of surface charge by alcohol (or
screening by adsorbed alcohol?) is only temporary, and if the masks were
tested a couple of days later, perhaps their efficiency might have recovered?

[https://search.proquest.com/docview/236317922](https://search.proquest.com/docview/236317922)

I would appreciate it if the Federal administration put some effort into
upping production of N95 masks for everyone - I've used them for years as dust
masks, and now they are not readily obtainable. I still have a small stash,
which we reuse and spray down with Everclear 151 after use.

