Kelly wrote:
I've been hoping I could find a relatively easy way to sterilise,
clean and reuse my coronavirus protection face masks, without the need
of powerful disinfectants and alcohol (which are of course also in
short supply). Then I came across this method online where a guy
reckons it's possible to do all this with just soap, hot water and a
toothbrush (it's almost as easy as washing your hands).
The guy plausibly (I thought) explains his method in a video:
https://diyjoy.com/how-to-sterilize-a-face-mask/
Could I please ask the 'experts' here in this newsgroup if they think
this is a good idea... or not?
Uh, oh. It's alive.
A strawman walks loose in the building, like a zombie.
Make it stop.
*******
All I can tell you, is "I pick disinfectant".
Preferably, a chemical that releases an oxidizer. Like a peroxide.
Something like peroxyacetic acid is used for surfaces.
https://en.wikipedia.org/wiki/Peracetic_acid
"Peracetic acid is always sold in solution as a mixture
with acetic acid and hydrogen peroxide to maintain its stability."
Damn. Well, that stinks.
https://www.iata.org/contentassets/7...sease-2019.pdf
"0.5% peroxyacetic acid, 3% hydrogen peroxide, or 500mg/L
chlorine dioxide can be adopted for air disinfection, by way
of aerosol spray, with 10-20ml/m³. Windows can be opened for
ventilation after 60 minutes of reaction. After spray disinfection,
the surface of objects may be wiped (swept) in the way of
daily disinfection."
Of course, you also don't want to be breathing that in later,
through the mask.
https://academic.oup.com/annweh/article/46/1/97/222610
*******
https://www.ctvnews.ca/health/food-i...safe-1.2923309
"High dose irradiation over 10 kGy can completely sterilize a food,
but is only used for products intended for those with severely
compromised immune systems."
Using that knowledge, a google gets me.
https://www.medrxiv.org/content/10.1...471v1.full.pdf
"Significant literature exists supporting the use of
gamma radiation as a sterilization method, with viral inactivation
of SARS-CoV reported at doses of at most 10 kGy,
with other studies supporting 5 kGy for many types of viruses.
However, concerns have been raised about the radiation
damaging the fiber material within the mask, specifically by
causing cross-linking of polymers, leading to cracking and
degradation during fitting and/or deployment
These results suggest against gamma, and possibly all ionizing
radiation, as a method of disposable N95 sterilization.
"
"Several methods of sterilizing N95 masks between uses are
currently being studied across the world. The advantages of
these methods and concerns regarding their use are summarized in Table 1.
Vaporized hydrogen peroxide and EtO treatments in particular
are described in detail by Viscusi et al (2009) [2]; UV treatment
procedures are described in Darnell & Taylor (2006) and Kumar et al (2015)
"
Hydrogen peroxide, when it breaks down, releases
H2O, so the "residue" happens to be relatively nice.
Just about any treatment, which is "hard on the lipid surface
of the COVID-19 container", likely also has a potential to
damage a synthetic fabric. Then it's a question of whether
the damage compromises the function of the thing.
When they sterilize the mail sent to the politicians in
Washington (the Post Office has some setup for this), it
"makes the paper crispy". Yet, this is what it takes to
keep people safe. The threat in these cases, is attempts
to send anthrax to politicians, as a dust inside an envelope.
Damaging the paper a bit, is the price they pay for this
bit of treatment.
Summary: You can see from the one paper, that they're interested
in making N95 masks last longer. But they're also not
fooling around. That's why they were seriously considering
gamma radiation. (You can't use that on lettuce because it
makes the lettuce wilt, but it's good on ground beef.)
Paul