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Enthalpy

Coffee filters as face masks?

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6 minutes ago, J.C.MacSwell said:

You certainly wouldn't expect the WHO, the CDC, or the US Surgeon General to have said that, would you? But you would be wrong.

 

From what I understand it is because of the risk of asymptomatic transmission coupled by the fact that there are a lot of undiagnosed cases in the US. I.e. it is not about not catching COVID-19, it is about not spreading it, which does not contradict what most have been saying before.

44 minutes ago, MigL said:

In my line of work, that could immediately endanger your life.
With Covid-19, improper use of a mask will endanger it 2 weeks later.

That is one of the worries when I see folks casually wearing certain masks (or gloves). I am not sure how big of an issue it really is but it feels "wrong" (based on my training in biosafety environments). I am seeing masks, cloths etc. as a portable sneeze guard more than anything, which is probably a good thing. It is just wrong to thing (IMO) that casual use will have protective properties, especially if folks then take more risks (as they think they are protected).

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17 minutes ago, CharonY said:

From what I understand it is because of the risk of asymptomatic transmission coupled by the fact that there are a lot of undiagnosed cases in the US. I.e. it is not about not catching COVID-19, it is about not spreading it, which does not contradict what most have been saying before.

 

That could certainly be the most important factor in them revising the guideline, the most important benefit that was being overlooked, but they are now admitting the benefit can be to the mask user as well. (which of course gives further benefit going forward to everyone else)

23 minutes ago, CharonY said:

It is just wrong to thing (IMO) that casual use will have protective properties, especially if folks then take more risks (as they think they are protected).

This is where I think we still disagree. If they are not taking more risks, just the ones they would take without a mask, I still think they are beneficial, and not insignificantly.

My opinion, which remains unchanged, is that it is wrong to think that casual use will not have protective benefits, unless folks then take more risks, whether by  thinking they are more protected than they are, or by mishandling the mask.

That said, I also still believe they should not be worn when it is clear the risks are effectively nonexistent. Better to breathe fresh air unobstructed. Along the same line of thought there are times I would prefer a surgical mask, or other lesser protective mask, to a more restrictive N95.

All that I think they would have understood from the start, if not for the emotional baggage of the mask shortage.

At least they are heading in the right direction.

 

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Should they make masks with one way valves, that only (mostly) filter on inhalation, illegal to wear in public? Or at least require the valves to be covered up?

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17 hours ago, J.C.MacSwell said:

Should they make masks with one way valves, that only (mostly) filter on inhalation, illegal to wear in public? Or at least require the valves to be covered up?

A little off topic: unless that's an option with coffee filters?

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3 minutes ago, dimreepr said:

A little off topic: unless that's an option with coffee filters?

Very much on topic. We've been comparing DIY type masks to other alternatives as to effectiveness for foth the wearer and the general public, due to scarcity of N95, surgical, and other masks. 

A "coffee filter" mask may be better at reducing the spread of virus by the wearer than an N95 with a one way valve.

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2 minutes ago, J.C.MacSwell said:

Very much on topic. We've been comparing DIY type masks to other alternatives as to effectiveness for foth the wearer and the general public, due to scarcity of N95, surgical, and other masks. 

A "coffee filter" mask may be better at reducing the spread of virus by the wearer than an N95 with a one way valve.

But you miss the point, that I tried to and failed to explain...

The topic doubles back when we try to protect ourselves: from what? 

Let's say I'm facing a fireing squad...

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I wasn't aware N95 masks had a one-way valve.
I use the 3M N95s and they don't have one. I assume you mean like on a half or full-face respirator.

23 minutes ago, dimreepr said:

But you miss the point, that I tried to and failed to explain...

I love you Dim, but you're still failing miserably to explain yourself :-) .

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Posted (edited)

I have 3M N95 masks with a one-way valve. I tried to upload a picture if it but it would not let me. It looks like the other 3M N95 masks but right in the center of the mask is an approximately one inch square, 1/3 inch depth, plastic piece with a plastic flap inside functioning as the one way valve.

I suspect it is no more likely to spread disease than the N95 without the valve, since the valve piece is attached to the mask material on the outside. Meaning your breath still passes through filter material prior to moving through the valve.

My mistake. I took a closer look and what I thought was filter material was NOT FILTER MATERIAL. It does indeed look like the valve allows my breath to freely escape the mask without passing through filter material.

Edited by zapatos

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Posted (edited)
2 hours ago, MigL said:

I wasn't aware N95 masks had a one-way valve.
I use the 3M N95s and they don't have one. I assume you mean like on a half or full-face respirator.

I love you Dim, but you're still failing miserably to explain yourself :-) .

Some do and some don't. The ones we generally use don't. We will be using full and half faced masks going forward (which we do anyway but now more so) as we donated most of our N95s (all without valves) to the local health authority, after they appealed to industry to "cough them up" (pardon the pun). 

Here is the valved type

image.png.e49889de0e4910e6d2c8c4354e492a99.png

I wonder if everyone using the valved ones will realize they are intended for protection of the user only. They should still help protect others, but not nearly as much.

Edited by J.C.MacSwell

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I have not really read it yet, but this article seems to reference some of the publications I have read on the subject: https://arstechnica.com/science/2020/04/should-you-wear-a-face-mask-heres-all-the-data-we-have/

So it could be a good read. A few seem to be missing, though.

Not sure if I referenced it before but there is also a review that is mostly focused influenza but also has (and criticizes) some SARS data: bin-Reza et al. (2012) Influenza and other respiratory viruses 6(4), 257-267.

Probably the overall outcome is that more studies are needed. 

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Learn something new every day.

But, for the life of me, I can't figure out  the need for the one way isolation valve.

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10 minutes ago, MigL said:

Learn something new every day.

But, for the life of me, I can't figure out  the need for the one way isolation valve.

Perhaps to help keep the mask a tight fit? So you breath in through the filter material, pressing it tighter against the skin, but you breath out through the valve so it doesn't break the seal against the skin. Maybe.

Or to prevent breathing out redistributing particles trapped in the filter?

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Yeah, the part I can't figure out is that, unlike cartridge respirators, an N95 mask doesn't really have a 'seal'.
Inhalating reduces pressure inside the mask, and pulls it closer to your face, sealing peripheral leaks.
Exhaling increases pressure inside the mask, and pushes it away from your face, allowing it to leak out from the periphery.
The whole mask functions as a one way valve.

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4 minutes ago, MigL said:

Yeah, the part I can't figure out is that, unlike cartridge respirators, an N95 mask doesn't really have a 'seal'.
Inhalating reduces pressure inside the mask, and pulls it closer to your face, sealing peripheral leaks.
Exhaling increases pressure inside the mask, and pushes it away from your face, allowing it to leak out from the periphery.
The whole mask functions as a one way valve.

I saw an interesting graphic showing which types of facial hair were compatible with face masks. So it seems that having a close fit against the skin is important. And if breathing out disrupts that, then perhaps that is a bad thing. Best hypothesis I could come up with.

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Posted (edited)

I generally prefer the N95s with the valve. The ones without them are more readily available and more economical. (why we mostly get them)

The advantages are that they are easier to breathe out through, moisture doesn't build up from your breath...and most importantly to me...your safety glasses don't get fogged up. The valve directs the flow downward.

A half face mask does all that as well, just a little bulkier.

Edited by J.C.MacSwell

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Yeah, exhalation through that disc is definitely easier than to breathe through your mask. In the lab we do not use them, but I found that even without a valve, if you can get the area around your nose bridge sealed off very tightly you can minimize fogging.

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Quote

The new study showed that while coffee filters are extremely effective at filtering microparticles, they score very poorly on the breathability scale, knocking them off the list of recommended DIY mask materials.

“Coffee filters, although very effective at filtering virus-sized particles, won’t make great masks,” Robertson said in the release. “They’re just too difficult to breathe through.”

Quote

Based on a combination of breathability and filtration effectiveness, the study recommended denim, bed sheets (80-120 thread count), paper towels, canvas (0.4-0.5mm thick) and shop towels for homemade masks.

https://www.yahoo.com/huffpost/best-coronavirus-face-mask-materials-new-study-120000624.html

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7 hours ago, zapatos said:

 

On 3/15/2020 at 9:26 AM, J.C.MacSwell said:

Have you tried them?

Properly sealed at the perimeter can you breathe through them without excessive effort? I would have thought not...

 

Besides the effort factor, the harder they are to breathe through the more air will get through a less than perfect seal at the perimeter.

Sometimes less is more.

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49 minutes ago, J.C.MacSwell said:

 

Besides the effort factor, the harder they are to breathe through the more air will get through a less than perfect seal at the perimeter.

Sometimes less is more.

They'll also become more obstructed with condensed vapour.

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I would think they don't really need to provide any 'filtering action.
More of a 'barrier' effect.

Recent data from Wuhan, suggests that only larger droplets from an infected person carry a viral load large enough to infect others.
The trace of one infected person, in a five story restaurant in Wuhan, with artificially circulated air throughout, found that infection was transmitted to nine others. But only from the same table or the adjacent one.
Smaller droplets which may be carried on circulating air currents don't seem to infect.
( but don't take a chance because I said so )

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Posted (edited)
5 hours ago, MigL said:

I would think they don't really need to provide any 'filtering action.
More of a 'barrier' effect.

Recent data from Wuhan, suggests that only larger droplets from an infected person carry a viral load large enough to infect others.
The trace of one infected person, in a five story restaurant in Wuhan, with artificially circulated air throughout, found that infection was transmitted to nine others. But only from the same table or the adjacent one.
Smaller droplets which may be carried on circulating air currents don't seem to infect.
( but don't take a chance because I said so )

That supports the minimum 2m rule. It also suggests to me that it's not so infectious as an aerosol.

Edited by StringJunky

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Posted (edited)
22 hours ago, StringJunky said:

That supports the minimum 2m rule. It also suggests to me that it's not so infectious as an aerosol.

Tell this to Diamond Princess passengers.. One infected individual was on board between 20 to 25 January. Taken to hospital and identified as infected by COVID-19 6 days later. 4 February cruise ship has been quarantined and people locked in their rooms the most of time. Three weeks later over 712 people were infected (some more identified after disembarking the ship)..

Edited by Sensei

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7 hours ago, Sensei said:

Tell this to Diamond Princess passengers.. One infected individual was on board between 20 to 25 January. Taken to hospital and identified as infected by COVID-19 6 days later. 4 February cruise ship has been quarantined and people locked in their rooms the most of time. Three weeks later over 712 people were infected (some more identified after disembarking the ship)..

And it's your contention that they were infected via aerosol while locked in their rooms?

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Big difference between one infected person socializing on a cruise ship for 5 days, and then who knows how many others he/others may have infected, socializing on a cruise ship for 14 days, compared to one infected person in a restaurant for 2-3 hours, in a fixed location.

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10 hours ago, Sensei said:

Tell this to Diamond Princess passengers.. One infected individual was on board between 20 to 25 January. Taken to hospital and identified as infected by COVID-19 6 days later. 4 February cruise ship has been quarantined and people locked in their rooms the most of time. Three weeks later over 712 people were infected (some more identified after disembarking the ship)..

Also note that estimates of the reproductive number on the cruise ships still indicate a fairly low transmission rate. That is consistent with limited airborne transmission (i.e. droplet transmission). If aerosol transmission was more common, more people would be expected to be infected, considering the timeline to detection.

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