Hello all, I'm a long time lurker but wanted to pass along this info I
found today on sterilizing masks. (This is particularly relevant to me as
I'm in NYC, and I was using rubbing alcohol in a spray bottle on my N-95
respirator until earlier today.)
As per a Stanford Medicine document dated March 22, baking N-95
masks/respirators at 70C is far superior to using alcohol (type not
specified) for disinfection. See pages 4/5 in the linked document for
summarized data on the effects of various disinfection methods on
filtration efficiency which leads to this:
Conclusions: DO NOT use alcohol and chlorine-based disinfection methods.
These will remove the static charge in the microfibers in N95 facial masks,
reducing filtration efficiency. In
addition, chlorine also retains gas after de-contamination and these fumes
may be harmful.
Source:
https://m.box.com/shared_item/https%3A%2F%2Fstanfordmedicine.box.com%2Fv%2Fcovid19-PPE-1-1?fbclid=IwAR2JY50gKPTJ4-7uR7nAw2aPEBrFp4B6v3WTi91S5A3WzADCl-QDG-PIfuA
Best,
Satadru
On Mon, Mar 23, 2020 at 4:13 PM Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
wrote:
On 3/22/2020 1:32 PM, William Claybaugh wrote:
Norman, Rand:
Please correct me if I’ve got this wrong but it has previously been my
understanding that only a Level 3 or better facility has in place
filters capable of capturing virus particles. This based on a visit
to a Level 4 facility.
I have previously understood that no face mask can filter virus
particles and that conventional face masks create, after a few minutes
use, exactly the warm and wet environment in which bacteria and
viruses thrive.
Technical point: Bacteria can thrive in warm and wet. Viruses require
living host cells they can hijack before they can reproduce. But yes, a
mask can trap and hold viable viruses.
So the thing to watch for in the current instance: do NOT touch the
exterior filter surfaces of a mask, while it's in use, or in removing
it, as it may well have collected some viable amount of virus. Handle
by edges or straps, then either dispose of (if you're lucky enough to
have plenty) or sterilize for reuse. And after you've been out where
you need a mask, after carefully removing the mask, immediately wash
your hands then the exposed parts of your face. If there's virus on the
mask there may also be some on exposed skin.
Laundering in hot water with plenty of soap/detergent works for cloth
masks. For paper, water (or steam) damages the fine paper structure and
greatly reduces filter efficiency. I've settled on a light spray of
isopropyl then air-drying thoroughly to stretch my limited supply.
(Rubbing alcohol in a dollar-store spray bottle.) Be advised I'm
guessing that's effective but can't prove it.
FWIW, I've seen a ref to hospital use of UV irradiation at a suitable
frequency being specifically effective for sterilization of nominally
disposable masks for reuse in the current emergency.
The utility of such masks for medical personal is—as I
understand it—only to avoid sputum in the air from coughing.
Is this all wrong?
Say, like much said on this matter, incomplete. Short version: Some
masks work better than other at reducing odds of either inhaling or
emitting a sufficient-for-infection dose of viruses. ALL work better
than no mask, as long as you avoid touching the filter surfaces
during/after use and sterilize the mask before reuse. And the net
effect for an individual of masking is reduced odds of either giving or
receiving infection. For a community, widespread masking usefully
reduces that community's R0. Not necessarily sufficient of itself to
reduce R0 below 1, but every bit helps.
IOW, people should stop letting "perfect" be the enemy of useful. Masks
are Part Of This Complete R0 Transmission-Rate Reduction Program.
Henry