Hi, we might want to try holding the LW-Cologne meetup at the Walled Garden. What should I do?
EGI
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Well, difficult at the moment. I would try the M3 6000 or 6500 series first since they are available in 3 sizes. But you basically have to shop around until you find something, which is difficult when most shops are sold out.
The interpretation I have for the mask is that we say y at any distance = mask rating (95 or 99).
This simple conversion does not work, since the drop of particle concentration over a certain distance is not fixed and drop size is not fixed. Under very favorable conditions you may get an infectious dose over 60 feet though that is quite unlikely.
But those filter materials may be something of a bottle neck too (and clearly do compete with providing masks to the medical workers.
That is my point. We should start manufacturing masks and filter material en masse NOW so we can provide everyone with a high quality mask in 2 to 3 months. Noone does this at the moment and what is produced is wasted on crappy one way products even most professionals do not use correctly.
I think it has more to do with N99 not being available in the filtering facepiece form which are the medical standard with very few exceptions.
Pretty sure. You should not get your filter wet though since this may allow diffusion across the filter, which is why it is unsafe to wear (N 95 or other) fleece masks for extended periods. Also stuff that is bound in the filter is also attracted via Van-der-Waals forces which are really strong on this scale.
Yeah, it will be way more than 99% of virus particles since most virus particles are bound in larger droplets where filtration efficiency is much higher than 99 %.
Adsorption air filters are not sieves or membrane filters, particles are captured by adsorption to the filter medium, not by size exclusion. The pessimum of filtration efficiency is afaik around 1 µm with higher capture efficieny below that due to higher collision probability due to more brownian motion. Not completely sure of the numbers though.
I’d go with P 99 or 100 since they are not that much more expensive / unpleasant to wear and we want to have as little particle leakage as possible since we do not know how much dose reduction is needed to reduce infection probability by one to two orders of magnitude. A hundredfold seems plenty though.
Also note that virus particles do not fly alone since they are allway bound in liquid or whatever remains after the droplet dries. CoV-2 seems to be nonviable when dried though so you need not worry about dry stuff.
Exactly, though we should aim to change that since protection would be improved while logistic demands would fall.
Also we should try to get governments to stimulate large scale production of such masks. See my original post.
This highly depends on mask quality and fit. A well fiting high quality oneshould be about as comfortable as a cloth mask.
I don’t have experience with US P99/100 filters but modern European P3 filters which are between P99 and P100 have hardly noticeable resistance.
1. This was the point of my original post. States should begin stimulating large scale production of masks and filters to provide most people with such masks.
2. No they don’t. Virus particles on the filter stay there as long as the filter does not get wet and decay quite quickly
3. Your mask either does not fit right or is low quality or has some kind of gas combination filter with very high flow resistance.
4. Yes, see discussion above.
See my reply to you above. That said, even if the virus was dry airborne as you assume, P3/N99 filters would still capture way above 99% of these particles as explained in my original post.
Yes, this mask is more of a symbolic pic, perhaps Simon can briefly explain why he chose this one (copyright issues I think). As explained in my original post and mentioned above you should use P3/ N99 or N100 filters.
Current understanding is that CoV-2 becomes nonviable when dried out Results form this study, though not in the document: (https://www.land.nrw/sites/default/files/asset/document/zwischenergebnis_covid19_case_study_gangelt_0.pdf).
Same guy stated it here: https://www.zeit.de/wissen/gesundheit/2020-04/hendrik-streeck-covid-19-heinsberg-symptome-infektionsschutz-massnahmen-studie/seite-2
They looked at about 100 infected households and sampled surfaces. Found virus RNA everywhere but NO viable virus. Also if that were false we would see airborne spread with people being infected over much larger spacial and temporal distance.
The public needs not be educated on what to wear, correct masks need to be provided by public private partnership (state money is used to stimulate large scale production) to stand a chance of equipping most people in a few month. You may want to use the original post linked.
Exactly! Mic and so on is not necessary and too complicated.
Yes, this is a drawback of any mask with exhalation valve. It is, as you suggest, easy to mitigate by covering the exhalation valve with cloth or a surgical mask. This is however imho not really necessary under most conditions, since the idea is to not get infected in the first place, so you do not shed any virus particles anyway.
Thanks for pointing these things out, I probably should have adressed them more.
… suprising that these masks are not in widespread use already.
I could think of several reasons for this.
Many (most?) health care professionals do not know of these masks or do not think of them as “medical equipment”.
People do not realize that filters can be used multiple times thus dismissing the idea as logistically impossible / even more expensive than FFP masks for everyone
People think that all masks do not work (well) to prevent transmission
People think that these masks are “overkill”, not realizing that a well fitting!!! reusable silicone mask is actually much less unleasant to wear than FFP masks.
… problems with compliance … unpleasant to wear for prolonged periods.
Yes, to a degree that is true. This should be addressed by...
Well fitting masks, at least 5 to 10 different types as discribed above with state of the art low resistance filters
Requiring people to wear masks only if there is actual risk of infection as described above
Rigorous enforcement especially in places where there are lots of people around (public transit, dense work places, schools and so on)
Hammer and Mask - Wide spread use of reusable particle filtering masks as a SARS-CoV-2 eradication strategy
You could just use your hands and wash/desinfect afterwards before touching your face. The virus cannot penetrate your skin and even lacerations are probably safe, since the target cells are in your nose/lungs.
Done.