Advice on mask-wearing to protect against Covid-19

I think this raises the question of what sort of evidence we should be looking for.

If I wanted to check that masks were protecting people, I'd get a plastic model of a person and give it artificial respiration (including moisture) from a sealed-off respiratory reservoir and have the dummy breathe in and out in a Covid-rich environment while wearing different types of mask (or no mask) and then measure how much Covid had made it through to the dummy's interior. Do mask manufacturers really not do that? If not, why not? It seems the obvious thing to do.

 

Oh yes, people have done lots of experiments like that and masks reduce virus transit under those conditions. The problem is that they bear a very indirect relation to real life.

 

That's interesting - I haven't been able to find that literature and wonder if it's publicly available.

 

I think it is mostly in technical publications.

 

I imagine they are quoting (wrongly) the most recent Cochrane review on masks - we do have a thread here on that review but my addled brain cant find it in this moment.

yes i did watch a video about this - that N95s dont work due to their thicker fabric but because of the way they are made with a charge that attracts particulates.

An N95/99 that fits snugly cant help but protect better than a surgical mask because at least some of the particulates will be attracted to the charge, in addition to it being thicker than and therefore giving more protection against the fluids containing virus that are released in coughs & sneezes.

This notion that N95s are no better than surgical simply cannot be accurate imho, based on the fact that surgical masks are so absurdly baggy i think they are bordering on pointless for the wearer. But people dont seem to realise that for an N95 to work it has to fit properly, not be touched by virusy fingers or taken off put in the pocket & then put back on again etc.

And the metal nose piece must be actually folded over the nose to make it snug... i just dont understand why people wear them so that air can get in all around, use them repeatedly after touching all the inside with germ covered hands, and then moan that they dont work... its common sense!

And surely they must protect others from the wearer - if they fit properly & have no valve - you've only got to see how damp they get inside after an hour of wearing - thats the wearers breath - which would be in the room otherwise surely?

I never go anywhere public indoors without my N95 on & i couldnt care less what people think. I also make sure to wear my large rimmed glasses - i read a study done on italian health care workers back in the early days - it was comparing people in same environments who wore eye protection plus masks with maks alone & the results were quite significant. I know glasses arent the same as visors but better than nothing i reckon.

The only exception is in certain Drs consulting rooms - if its important they dont suspect me of health anxiety, there's a little ventilation, & neither they nor their nurse appears to have any symptoms... then i take it off, & then put it back on to go through waiting area & common areas. This is risky, but currently because of the other dx i have on my notes... getting pegged with HA as well, would be just as risky to me overall, even if in a different way.

It makes me laugh at my gp surgery though... they ask everyone to wear a mask, but the gp pulls her surgical mask down to talk to me... i mean why even bother wearing it at all? I guess she pulls it up if she hears someone coughing.

 

Completely false. N95s filter small particles effectively. They are rammed into the filter material by Brownian motion.

 

Also, masks can't fit every face. They're good, but when I was using them even the best I could buy left small gaps at two places on each side. I could adjust them to the optimum position when I went out, but as soon as I'd had to move my face to speak, there was a slight shift.

 

Thanks, @RedFox. Do you have any refs? I'd like to study this stuff a bit.

 

I hastily found this paper which discusses how particulate filters work: An overview of filtration efficiency through the masks: Mechanisms of the aerosols penetration. They're not like screens that only catch particles smaller than the screen. They trap larger particles by screening them, but they can still trap particles smaller than the distance between fibers via an effect that only happens at tiny scales: Brownian motion. All the molecules of air are moving at different speeds, and when a small particle gets struck by a particularly fast air molecule, the collision makes it abruptly change course, like a billiard ball being hit by a cue ball. Each time this happens, the particle has a chance of being shoved off course into the filter material.

If I recall correctly, N95 masks/filters are rated for their performance at 0.3 um because this size is (or was) one of the hardest to filter--small enough to slip between the fibers, but big enough to not get beaten around too much by Brownian motion.

 

My understanding has always been that masks do not really protect the wearer, but primarily protect others from the larger droplets expelled when you cough, splutter, sneeze etc. So by no means foolproof, but a beneficial contribution to the numbers game. I seem to remember that was the main message early on in the Covid outbreak, wear a mask to protect others.

 

That's also completely and utterly false, it's misinformation pushed by the CDC in the early stages of the pandemic. Let's first look at a few terms:

• Source control: Preventing an infected person from spreading to others.
• Infection control: Preventing the wearer from getting infected. Good infection control provides excellent protection to others because You cannot transmit a virus you do not have.

• Low-effectiveness masks like cloth and surgical masks provide a little source control and very little infection control. This is because they have a poor fit and cannot filter fine particles well. Particles and droplets are bigger immediately after being exhaled because they haven't dried out yet. That's why these masks are better for source control.
  
• An N95 with no exhalation valve provides excellent source and infection control.
• An N95 with an exhalation valve provides excellent infection control but only a little source control.

Through the entirety of the pandemic, I wore masks with exhalation valves. I had no guilt about this. Early on, I cared primarily about protecting myself because I considered myself vulnerable, and I knew I couldn't transmit an infection I couldn't get. Later, nobody cared about being protected anyways.

 

I wish I'd done this - i.e. mask wearing - last week when I went to the theatre, then I might not have got &%£^£%^ Covid! It's still out there, folks.

 

When cases (per wastewater locally) are low, then I will linger in indoor spaces but with a mask.

At the moment cases where I live (per wastewater calculation) are deemed moderate. I won't stay inside for more than a few minutes when there are people about. Of course, I have on an N95.

If a place is crowded with people, and the level is moderate or higher, I just won't go in, unless absolutely necessary.

There has only been two weeks (in the past almost 4 years) when i went into the small grocery store unmasked.

I just can't afford the chance of long covid or a bad case of covid.