Efficacy of homemade masks

Disclaimer: I'm no expert on this. I only know what I think I know to be true, and am analyzing this study to the best of my ability.

I was talking with someone today who insisted that homemade masks were a stupid idea and, "will do absolutely nothing to prevent you from getting the virus." I disagreed insisting that an imperfect filter is commonsensically better than no filter. He was not convinced. So after some googling, I found this study from 2010.

Simple Respiratory Protection—Evaluation of the Filtration Performance of Cloth Masks and Common Fabric Materials Against 20–1000 nm Size Particles

About the scientists (now, not 10 years ago)
Samy Rengasamy - Physical Scientist at Centers for Disease Control and Prevention
Benjamin Eimer - worked for four years as an aerosol physicist for NIOSH as a government contractor
Ronald E. Shaffer - 20 years of experience conducting laboratory and clinical research and leading teams performing applied R&D in a variety of fields including public health, infection control, medical devices, homeland security, nanotechnology, and chem/bio defense.

Common fabric materials of five major categories including sweatshirts, T-shirts, towels, scarves, and cloth masks were selected for aerosol penetration tests... Fabric materials for each category were randomly selected from three different manufacturers based on availability. The commercial cloth masks were advertised as pollution and allergen masks and did not make any claim as to their effectiveness for submicron-size particles. It should be noted that none of the other fabric materials was designed to be used as a filtering media. N95 respirator filter media was tested in parallel with the fabric materials for comparison of the filtration performance against submicron-size aerosol particles.

They tested common materials from Hanes, Dickies and other companies, as well as pollutant masks and also N95 respirators. For reference, Covid-19 has a diameter of 60-140 nm.

RESULTS
...
Monodisperse aerosol penetrations
Penetration levels for monodisperse aerosol particle (20–400 nm range) were combined with those for 500–1000 nm range particles measured as a function of particle size. For the cloth masks, monodisperse aerosol penetration levels (35–68%) for 20 nm size particles increased steadily, reached maximum (73–82%) at 100 nm range, plateaued up to 400 nm, and increased slightly up to 1000 nm at 5.5 cm s−1 face velocity.

This confuses me, so perhaps someone can explain. Why does penetration increase when the size of the particle increases? Shouldn't it be the opposite? I thought maybe penetration level was a good thing based on these numbers, but they mention, "filtration efficiency...inverse of the penetration," so this is not the case.

Penetration levels for the three sweatshirt and T-shirt models were, respectively, in the 30–61% and 56–79% ranges for 20-nm size particles and increased to 80–93% and 89–97% for 1000 nm particles

Again, larger particles get through more (?) but 20nm particles have penetration levels as low as 30%!

In the case of towels and scarves, penetration levels varied from 9 to 74% for 20 nm size particles and increased monotonically at 5.5 cm s−1 face velocity. Penetration levels of different size particles increased at 16.5 cm s−1 face velocity at varying levels

As low as 9%!

Perhaps I'm reading all this wrong, so please someone tell me if this is the case. It's been so hard to find any recent information that can be trusted. And though I don't really watch the MSM, I haven't heard anyone really talk about what homemade masks should be made from. They just say, "make your own at home from t-shirts and other fabrics." If sweatshirts are really up to 50% more effective than t-shirts, people should be told!

Bottom line, I think it's stupid to think that a homemade mask won't filter at least a small percentage of aerosols, and I think it's stupid to not be wearing a mask anytime you leave the house. They are very easy to make, and wearing one certainly won't harm anyone. And if this is all a hoax, it's only gonna cost you a couple articles of clothing.

I think that homemade masks offer more protection from "you" than for "you."
If you get my meaning.

Either way, like you said, it can't hurt.

a reply to: scojak

Buy vacuum bags that are HEPA filtered, then cut the vacuum bags to insert into your mask.

a reply to: Phage

Absolutely. You are filtering at the source. But a filter goes both ways, so it's definitely not useless for stopping what's trying to come in.

a reply to: scojak

I was talking with someone today who insisted that homemade masks were a stupid idea and, "will do absolutely nothing to prevent you from getting the virus."

Yeah, the idea is more to protects others from you, than to protect you from others.

Especially if you are an asymptomatic carrier.

a reply to: DBCowboy

Genius! Maybe I'll buy some Hoover stock options on Monday

How to make your own face mask


link

I guess just getting a scarf might be easier

a reply to: scojak

I was talking with someone today who insisted that homemade masks were a stupid idea and, "will do absolutely nothing to prevent you from getting the virus." I disagreed insisting that an imperfect filter is commonsensically better than no filter. He was not convinced. So after some googling, I found this study from 2010.

Absolutely. Even basic masks have been shown to be effective in slowing transmission. Especially as Phage said, from you more than to you. Here is a link to several studies. Effectiveness of basic masks

This confuses me, so perhaps someone can explain. Why does penetration increase when the size of the particle increases?

Saturation of the filtering material would be my guess.

It's just a matter of time until the NY clothing designers make masks an accessory item. Frilly lace for the ladies and a masculine leather border for the guys and heavy duty buckles and leather straps to keep it snugly against your face and perhaps that polo logo to impress all the rabble just wearing that low class paper thing or a ghetto bandana.

Little prints with puppies and kitties for the children. Les't not forget man's best friend either.

personally I'm going completely 420 and duct taping a coffee filter to my face and filling the cracks with gorilla glue. Better safe than sorry!!

originally posted by: Klassified

This confuses me, so perhaps someone can explain. Why does penetration increase when the size of the particle increases?

Saturation of the filtering material would be my guess.

Interesting. I hadn't thought of that.

a reply to: scojak

In the instant you think you are safe from this virus, and then expose yourself to an infected host ... you've got it.

What is still not at the forefront of the common man's understanding of this threat ... is how extremely contagious it is.

This virus is a human-engineered bio-weapon. And, never forget that it was the Chinese who unleashed it on all of humanity.

ETA: Specific to the viability of any mask: If a mask is protecting you from the virus ... you are gonna suffocate. You need a machine pumping air to you for something like that to work.

I 3D printed some masks in TPU plastic from an online design. Instead of the provided filter design, i designed an alternative filter housing. I use cotton make up pads as filter material, cheap and available. 100% ? No.

But indeed better as nothing and easy replaced. ( Do take care of handeling )

Here is a page that shows the data from the University of Edinburgh test of masks. It includes data of cotton handkerchiefs.

Be sure to read the comments as there is additional information and links in them.

smartairfilters.com...

More about efficacy between n95 and surgical masks.
smartairfilters.com...

It's doesn't matter what kind of mask you wear if you are always adjusting it to make it feel comfortable touching your face and then rubbing your eyes.

originally posted by: olaru12
It's doesn't matter what kind of mask you wear if you are always adjusting it to make it feel comfortable touching your face and then rubbing your eyes.

Good point. You won't be doing yourself any favors by touching your face and adjusting the mask, but it will still help protect others from you.

originally posted by: olaru12
It's just a matter of time until the NY clothing designers make masks an accessory item. Frilly lace for the ladies and a masculine leather border for the guys and heavy duty buckles and leather straps to keep it snugly against your face and perhaps that polo logo to impress all the rabble just wearing that low class paper thing or a ghetto bandana.

Little prints with puppies and kitties for the children. Les't not forget man's best friend either.

In east Asia, like Japan for isntance, face masks have been a major accessories business for years. Wearing a mask while you're sick is much more ingrained culturally there than it is here. You can see this on U.S. college campuses, where in the flu season you'll often see Asian students wearing masks. To make it appeal to younger people, there are a bunch of companies that make novelty masks so people don't have to walk around wearing a generic-looking one.

originally posted by: olaru12
It's doesn't matter what kind of mask you wear if you are always adjusting it to make it feel comfortable touching your face and then rubbing your eyes.

Quite true. Same applies to if you wear gloves. Your hands might be protected, but everything you touch with your contaminated gloves isn't!

Seems strange that we even have to tell people these things. You'd think that would be rather obvious to anyone.

originally posted by: DBCowboy
a reply to: scojak

Buy vacuum bags that are HEPA filtered, then cut the vacuum bags to insert into your mask.

HEPA filters are made from glass micro fibers which are bad for the lungs and us sewers are now being told not to use them.

Info is changing so fast on what we should/shouldn't do, it's hard to keep up.

originally posted by: nugget1

originally posted by: DBCowboy
a reply to: scojak

Buy vacuum bags that are HEPA filtered, then cut the vacuum bags to insert into your mask.

HEPA filters are made from glass micro fibers which are bad for the lungs and us sewers are now being told not to use them.

Info is changing so fast on what we should/shouldn't do, it's hard to keep up.

Seems like that should be spread around a lot of places quickly, cause I can imagine a lot of people trying that.

a reply to: scojak

Homemade masks are less effective against 0.1nm particles than specifically designed membranes. However, they do a solid job against globs of spit and snot shooting out of your mouth and nose on which the CV hitches a ride.

Plus you can sew up some really cool looking fabrics. It's important to maintain high fashion sense during the apocalypse.