What are the best materials for making a DIY ~0.3 micron mask at home to filter in the coronavirus?

[Arlen Holder]

Is constructing a ~0.3 micron filtered face mask on-topic for a.h.r?

If so, here's my DIY design today based on the suggestions in the NYT:

1. I didn't have hair ties, so I used Costco chicken elastic, doubled over.
2. The ~0.3um particle filter is a rectangle of vacuum cleaner bag cloth.
3. The cotton bandana is simply to comfortably hold the filter to the face.

o It's Time to Make Your Own Face Mask

o What's the Best Material for a Mask?

o What Are The Best Materials for Making DIY Masks?

o Can DIY Masks Protect Us from Coronavirus?

Notice dish towels & vacuum cleaner bags aren't all that bad. o Also doubling up on layers doesn't do help all that much.

Mostly, these Covid-19 masks keep the virus "in", and not "out", where the virus is, of course, smaller than 0.3um (which is the size of the carrier), where the actual virus is on the order of smaller than 0.1um, but at that size, due apparently to Brownian motion and other effects, particles that size bounce around more to hit the filter media.

More details are in the article above, where this thread is just for ideas on making a quick but effective home DIY SARS-CoV-2 droplet filter mask.

[hubops]

Mine was quick & cheap & disposable :

A wire-tie taped on for a nose-clamp was an afterthought .. It fits quite well, and adjustable by trimming with scissors < for child size >

John T.

[Clare Snyder]

The average coffee filter is 12-50 micron - and a lot of the cheap ones closer to 100 micron.The coroma virus is .06 to .14 microns. How effective is that coffee filter mask???

A HEPA filter filters to .3 micron - but due to Brownian Motion can catch SOME particles down to roughly .15 microns - due to turbulence in fluid flow and possibly electrostatic attraction.

An N95 catches 95% of particles down to .3microns An active HEPA filter catches 99.7 of particles at .3microns.

If I need to make masks I'll use the Hepa filterr bags for my CanaVac central vac. 99.4%.

[hubops]

D I Y masks are not about protecting the wearer - it's about keeping the wearer's spit drops off of things. How many microns in a spit drop ? sneeze drop .. John T.

[Clare Snyder]

5 to 15, generally speaking - for aerosolized sneeze - so still not very effective. Might reduce the range by a few percent though - - - -

[Arlen Holder]

Hi John T,

Given the goal is to design and build an effective mask at home...

Thank you for showing your use of the coffee filter material in your photo! o Googling, I found the CDC also recommends we use coffee filters!

o *Use of Cloth Face Coverings to Help Slow the Spread of COVID-19*

I saw Clare's subsequent post about the size of the filtering, where it seems we need to look up the scientific details on how they work on droplets containing the SARS-CoV-2 virus.

Slate says the SARS-CoV-1 coronavirus is about 100 nanometers (~0.1um): o *Do Surgical Masks Stop the Coronavirus?*

But, of course, the virus isn't what we're filtering - we're filtering droplets which contain the virus, where those droplets are far larger. o Can DIY Masks Protect Us from Coronavirus?

"The DIY masks captured fewer particles than the surgical mask, but they still managed to capture 69% of 1-micron particles."

"The researchers stepped it up a notch by shooting .02-micron Bacteriophage MS2 particles at the masks. These are even smaller than coronavirus particles. Again, the surgical mask captured more particles, but the homemade cloth mask captured 51% of these nanoparticles."

"Across 21 volunteers, the homemade cotton masks captured 50% of 0.02-1 micron particles, compared with 80% for the surgical mask. Thus, DIY masks still managed to capture particles while people were actually wearing them. Based on this data, the researchers concluded that homemade masks would be better than nothing."

Of course, if it only takes a few particles to get us infected, I'm not sure what the real benefit of blocking half of them might be.

Do we know the minimum dosage that gets us infected? o For example, could it be as low as a single virion?

[Cindy Hamilton]

The best materials for making a mask are ones you have on hand. If all you have is a bandanna, then that's the best material.

A co-worker who is not particularly handy (by my standards, at least) discovered he had a couple of N95 masks left over from refinishing some furniture.

Cindy Hamilton

[Arlen Holder]

The virus itself, is huge for a virus, but still pretty tiny, around 100nm, or about 0.1um (approximately, to round numbers).

But what matters is the "spit" size, which, if it's 5um to 15um, then that's what we need to filter "in" when we're at close quarters.

One problem, as noted prior, is whether it's at all useful shielding "most" of the particles, where it could be like machine-gun bullets, where only one needs to get out to infect someone else.

Still, the news is abuzz with home-made DIY mask designs, such as this: o *How to make a non-medical coronavirus face mask ¡V no sewing required*

In that article, sans sewing, they make a mask out of an old T-shirt, with a paper towel as the absorbent central material.

This (clickbait?) news article says an unpublished paper reports: "Quilters¡¦ cotton, a tightly woven high-thread-count fabric, can filter out some 70% to 79% of small particles including viruses... ' That's better than surgical masks, which Segal said filter out only 65% of particles. (N95 masks offer the highest level of protection filtering out 95% of air particles.) o So what materials do come out on top?

"Vacuum cleaner bags ranked higher than tea towels, but they¡¦re considerably more difficult to breathe through"

And yet: "Tea towels are better to use for a mask than T-shirts or pillowcases" o *Addressing COVID-19 Face Mask Shortages* (Stanford Medicine)

There's another simple design in MarketWatch over here: o *When you can¡¦t buy a mask, make it yourself*

[dpb]

On 4/7/2020 11:01 AM, Arlen Holder wrote: ...

...

Of course it's useful; anything that minimizes the distribution of a given number of individual virus that are spread or reduces the population of those being spread is of benefit.

Only talking in what percentage of effectiveness is...

[Thomas]

I just wear 2 real masks at a time.

[Arlen Holder]

Let's try to be scientific if we can...

I'm not sure if you're joking as I didn't see a smiley, but if not, then recall that one of the references I quoted tested multiple layers, finding two layer much more effective than a single layer, for a variety of reasons.

We could dig up that reference, but I only point out that potential logical fallacy of "doubling up", simply because now that the hoi polloi are wearing face masks en masse, all the silly thought processes of non scientific humans will be taking root as old wives tales.

At Costco today, I'd estimate over 85% were wearing masks in the store:

I wonder if they all fully realize what "direction" the masks are supposed to protect? (just like with the "baby on board" signs)

BTW, this was what a guy at Costco was wearing today... where, let's remember, the mask is, just like those baby-on-board signs, pointed in the wrong direction for most people to comprehend what it actually accomplishes. :)

The whole point is to be scientific about the problem set.

[Davej]

Yeah, 95 + 95 = 190% of particles.

I ordered some HEPA vacuum bags but apparently they are stuck in some mailroom somewhere. I since have read that HEPA filter material needs to be used with caution because they usually contain micro-particles of glass fibers -- especially if you cut the material. Another safer material that is suggested is Halyard H600 sterile wrap.

But don't most of us already own an ordinary painting and woodshop-style

3M mask?

[Arlen Holder]

To claim "of course it's useful" must mean that you've assessed the facts, where I have seen grown scientists seriously debate whether even the N95 mask is useful, let alone the DIY masks we're gonna make.

Given, oh, say, trillions of viral particles in a single sneeze (maybe only billions?), and given only about 20% to about 60% of the particles are captured by the DIY masks - and given that it may take only a single droplet to infect someone, I'm not so sure as you are that "of course" it's useful.

IMHO, it _may_ be useful; it might not be. o We'll only know from actual science and not from intuition.

Certainly the use of masks, en masse, by the hoi polloi, has been debated in the scientific community in the past few months, where it takes time for a scientific consensus to emerge.

[Davej]

Ideally grocery stores should be on warm tropical islands with open outdoor markets and large electric fans blowing air down the isles, but all we have are the masks. If they reduce the droplets they are doing something in your favor. Wear your scuba gear if you are too worried. The best solution is to stay home in your basement.

[micky]

They, even someone here, claims those paper masks are only good for one use. Of course that's an 8 hour day, and i only wear mine for 30 minutes to go to the grocery store, so I get 16 trips, and more if it hasn't fallen apart.

[Clare Snyder]

Doesn't work that way Mick

[Clare Snyder]

That's like saying you can use a condom numerous times with numerous partners, as long as it hasn't split - --

[Arlen Holder]

Speaking of wearing protection in a car, I should have snapped photos, but on my way back from Costco, I saw _numerous_ people wearing the stuff in the car.

Note that one of the references I quoted specifically says not to wear the mask in the car, which we can dig up for more details.

The key point though is that the _science_ is what matters in terms of what materials we make the DIY mask out of, and what use model we employ.

For example, it's fallacious, IMHO, from the standpoint of what the mask is designed to do, for someone to count wearing it ten times for three minutes as the same as wearing it once for a half hour.

There are _other_ factors involved, such as proper hands-off donning & removal procedures (which all surgeons are well aware of, for example).

[Arlen Holder]

Maybe. Maybe not. o For example, does wearing a bullet-proof suit protect an infantryman?

"Of course", right? o But then, why don't infantrymen always wear a bullet-proof suit?

My point is that the "of course" assumption was purely intuitive..

Whether or not it's pragmatic or even scientific valid, remains to be seen, which is why we ask for facts in this thread on how best to build a DIY mask that actually does the job it's supposed to do.

Think about what you just said. o Do you see the fallacy in your argument?

That same fallacy is the reason I posit those "baby on board" signs are pointed in the wrong direction.

As to your fallacy, I know some of the respondents to this thread indicated they do know _why_ we're wearing the masks. o But it seems you don't seem to understand (based on your statements).

Think about it for a moment... o Do you see the fallacy in your argument about "me" wearing scuba gear if I'm worried about the virus?

I hope so, as a _lot_ of people don't seem to realize what the masks do.

[Cindy Hamilton]

I put my cloth mask on at home and take it off when I return, AFTER washing my hands. It would be crazy to take it off in the car.

Cindy Hamilton