A team of researchers have tested everything from t-shirts and socks to jeans and vacuum bags to determine what type of mask material is most effective at trapping the ultrafine particles which may contain viruses such as SARS-CoV-2, the virus which causes COVID-19.
The researchers, from the University of Cambridge and Northwestern University, tested the effectiveness of different fabrics at filtering particles between 0.02 and 0.1 micrometers – about the size of most viruses – at high speeds, comparable to coughing or heavy breathing. They also tested N95 and surgical masks, which are more commonly used in healthcare settings.
“It’s a matter of finding the right balance – we want the materials to be effective at filtering particles, but we also need to know they don’t put users at risk of inhaling fibres or lint, which can be harmful.” — Eugenia O’Kelly
Previous studies have only looked at a small selection of fabrics when the wearer is breathing normally, when particles are expelled at lower speed. Studying more fabrics and testing them at higher speeds provides a more robust evidence base for the effectiveness of fabric masks.
The results, reported in the journal BMJ Open, show that most of the fabrics commonly used for non-clinical face masks are effective at filtering ultrafine particles. N95 masks were highly effective, although a reusable HEPA vacuum bag actually exceeded the N95 performance in some respects.
As for homemade masks, those made of multiple layers of fabric were more effective, and those which also incorporated interfacing, which is normally used to stiffen collars, showed a significant improvement in performance. However, this improvement in performance also made them more difficult to breathe through than an N95 mask.
The researchers also studied the performance of different fabrics when damp, and after they had gone through a normal washing and drying cycle. They found that the fabrics worked well while damp and worked sufficiently after one laundry cycle, however, previous studies have shown that repeated washing degrades the fabrics, and the researchers caution that masks should not be reused indefinitely.
“Fabric masks have become a new necessity for many of us since the start of the COVID-19 pandemic,” said first author Eugenia O’Kelly from Cambridge’s Department of Engineering. “In the early stages of the pandemic, when N95 masks were in extremely short supply, many sewers and makers started making their own fabric masks, meeting the demands that couldn’t be met by supply chains, or to provide a more affordable option.”
While there are numerous online resources that help people make their own masks, there is little scientific evidence on what the most suitable materials are.
“There was an initial panic around PPE and other types of face masks, and how effective they were,” said O’Kelly. “As an engineer, I wanted to learn more about them, how well different materials worked under different conditions, and what made for the most effective fit.”
For the current study, O’Kelly and her colleagues built an apparatus consisting of sections of tubing, with a fabric sample in the middle. Aerosolised particles were generated at one end of the apparatus, and their levels were measured before and after they passed through the fabric sample at a speed similar to coughing.
The researchers also tested how well each fabric performed in terms of breathing resistance, based on qualitative feedback from users. “A mask which blocks particles really well but restricts your breathing isn’t an effective mask,” said O’Kelly. “Denim, for example, was quite effective at blocking particles, but it’s difficult to breathe through, so it’s probably not a good idea to make a mask out of an old pair of jeans. N95 masks are much easier to breathe through than any fabric combinations with similar levels of filtration.”
In preparation for the study, the researchers consulted with online sewing communities to find out what types of fabric they were using to make masks. Due to the severe shortage of N95 masks at the time, several of the sewers reported that they were experimenting with inserting vacuum bags with HEPA filters into masks.
The researchers found that single-use and reusable vacuum bags were effective at blocking particles, but caution that the single-use bags should not be used in face masks, as they fall apart when cut, and may contain component materials which are unsafe to inhale.
“It’s a matter of finding the right balance – we want the materials to be effective at filtering particles, but we also need to know they don’t put users at risk of inhaling fibers or lint, which can be harmful,” said O’Kelly.
The researchers caution that their study has several limitations: namely, that they did not look at the role which fit plays in filtering particles. In a related project, O’Kelly has been studying how the fit of masks in healthcare settings can be improved. In addition, many viruses are carried on droplets which are larger than those looked at in the current study.
However, O’Kelly says the results may be useful for sewers and makers when choosing which fabric to use for making masks. “We’ve shown that in an emergency situation where N95 masks are not available, such as in the early days of this pandemic, fabric masks are surprisingly effective at filtering particles which may contain viruses, even at high speeds.”
Further information about the research can be found at: www.facemaskresearch.com
Reference: “Ability of fabric face mask materials to filter ultrafine particles at coughing velocity” by Eugenia O’Kelly, Sophia Pirog, James Ward by P John Clarkson, 22 September 2020, BMJ Open.
It’s amazing that only the recent studies that show the effectiveness of wearing face mask to reduce the spread of the coronavirus are being published and none of the 50 odd previous studies all done by reputable institutions clearly showing that they don’t work are not even being mentioned. I consider this to be deliberate and manipulative..poor use of journalism.
This is fake science. There are no studies that contradict the use of masks to prevent infection. Real scientists don,t say things like that. Real scientists would list the studies so you can read the evidence yourself. Fake Fake Fake
I would rather be wrong than dead, why is it such a divide in wearing a mask and it could possibly keep yourself safe and your fellow citizens. This is crazy that people think in order to support the president they have to be reckless with science. Just like wearing seatbelts it would not help the person in the other car if you don’t have your seatbelt on it would not matter at all if your the one flying through the window cut in half but yet it’s not this much resistance wearing them and you will get a huge ticket if you get caught driving without one, I know. This president is reckless and very selfish because the things he’s pushing he’s not following at all. If you go around him you still have to test but yet he swears against test and anyone close has mask on but yet he said that 85% mask wearers have caught coronavirus and that’s another lie. And when he caught the plague he hurry up and ran to Walter reed and had up to 14 doctors paid by our tax dollars to fix him up he was given medicine that we won’t see for another year and two years before it’s available. But what’s funny is he didn’t take that hydroxychloroquine as a matter of fact you didn’t hear him mention that deadly meds when it’s used wrong for his own treatment,2 people died listening to this selfish man using a medicine not made for Coronavirus and he didn’t even have enough compassion to mention these people. I don’t care if people support a selfish racist that doesn’t care about anyone but himself but at least you can wear a mask.Who cares if it’s not 100% fool proof because if it helps a save a few lives it’s better than nothing. And I am serious when I say who cares if you support him even though this man is racist as hell and here we live in a country that has gotten so far ahead of other countries in self growth and I’m a black woman and what I have saw in my country is sickening. I thought we were growing but Trump has exposed alot of these white people true feelings and it’s sickening but with all that, just wear a mask.
The White N95 mask nearly killed me. I was not getting oxygen and was collapsing.
Anti-maskers love to cite “odd” studies without specifically referencing then so they can justify selfishly trying to kill me and my loved ones. However, would those same mask haters go to a dentist who doesn’t wear a mask? I doubt they’d want such a stranger in their face without a covering. What I’d really like to see is an anti-masker send their spouse, parent or child into a surgery theatre with an unmasked surgeon. If masks are so worthless then certainly they would have no trouble with offering themselves or their loved ones up to be opened up with a scalpel by an unmasked surgeon. Yeah right, let an unmasked dentist or surgeon get near them or their family and they’d scream bloody murder. Wanting it both ways is hypocrisy, and wanting me to wear my mask to protect them whilst shoving their uncovered face and spittle at me is the worst form of selfishness.
A visit to the dentist or having surgery isn’t the equivalent of a trip to the grocery store. Nobody should be hovering over you that close while shopping. Sounds like you need to live in a sanitized bubble and not venture out to “protect” yourself and family. Also note the article touched on not mentioning fit…something the vast majority of mask wearers ignore or are unaware of.. anything besides tight properly fit masks = useless pieces of material.
I’m over 50 and I’ve never seen a dentist wearing a walk. What world do you live in?
Here’s a CDC review of 14 PPE random control trials testing the effectiveness of PPE on transmission rates of flu-like viruses. This is actual real science that includes control groups and test groups. Just read the abstract and find out the truth. You can also scroll down to the section on face masks and get even more detail. As well, the CDC provides links to all the RCTs source documents.
So many studies miss the most effective and cheap filter material, non-woven melt blown fabric, the same material used to make surgical masks. It can filter out very small particles without restricting air flow. It is also very cheap. You can buy in 10s of yards and cut up in to 4″ x 5″ filters, each filter cost only about 10 cents.
Available from Amazon and eBay
If I can smell your breath in spite of your mask, it’s not helping.
I think in this case you need better toothpaste or better teeth hygiene
You can buy them everywhere, different clothes and prints so just wash it out and s use a new one to match ur clothes& outfit so we can get this undercomtrol. Stop wearing the same mask over & over. Thats grose
If everyone wore a mask properly and don’t be right on top of one another maintain social distancing and avoid large gatherings we just might have a better chance of getting a handle on this virus have respect for human life and yourself people are so disrespectful when you’re somewhere indoors with signs posted must were mask and still don’t it’s not fair and we’ll never get a handle on this virus it all starts with yourself be respectful to others please this is very important to humanity as we know it.
Wasted article – aka “click bate”
I have a question, when visiting asbestos abatement projects a N95 was not approved by OSHA for use. Asbestos is 1-10 microns. And covid is reported as.125 microns. How is a N95 protecting me? Form.anything other than someone’s spit?
It’s great this article claims they tested different materials. You know if the scientists thought this info was important they would have given the results. Then they say well we asked some random people seeing masks what to use. That’s not a scientific study. Nothing in this sounds scientific. Most of the air from a mask goes right around the mask. I know when I wear those masks doing carpentry, I get a mask full of sawdust and have to blow sawdust out of my nose. A neck gaitor doesn’t allow any sawdust through. That’s the only thing you should be wearing. A mask just over your nose and mouth doesn’t work well unless it fits very snugly and only kind of good then.
Just so you know I’ve been to a few hospitals since this started for different reasons. In NJ only about half the hospital workers were wearing masks (where they’ve already had another lockdown from fear of an insect at the time) The woman working triage wasn’t wearing one. The ambulance drivers and emts weren’t wearing them. They only gave me a mask to enter the hospital then had me take it off and on as they did stuff. The doctor had some high tech full face mask I’ve never seen. Basically everyone has different opinions and if in the hospitals they aren’t wearing masks why should anyone else? It’s to train us to be compliant. We are tired of being treated like cattle. I wear a mask so others feel safe. I don’t believe they do much but I wear one. That’s part of being in a society, it’s not one of the good parts. Too much of this and society will break down, I mean more than it has already.
Why are all patriots braindead meatheads that draw reasoning from their observations and only from THEIR
The doctor in China who tried to notify the world about SARS-CoV-2 wore two masks. N95s. Look at the photos of him. He still died. The homemade masks that you touch, take-off… often will kill you.
Just because he had two masks on (which doesn’t even make sense because they won’t fit correctly on your face) it doesn’t mean that he wasn’t infected before he decided to wear them. Obviously there was a time when he didn’t know how bad covid-19 was.
Sigh…anti-matter DT worshipers who love Trump’s America where they can live the life of caring about no one else but themselves…just like their idol.
Why is it anti makers turn away the science of breathing someone else’s germs. You are as irresponsible as your leader. Karma is a bitch and god help his arrogance. He WILL pay.
The CDC did a review of 14 PPE random control trials (actual real scientific studies that include control groups and test groups). Ten of these RCTs tested face masks. All 10 RCTs had the same results: face masks DO NOT reduce transmission rates for flu like viruses. IN FACT, CLOTH MASK MAY ACTUALLY INCREASE TRANSMISSION RATES.
Here is a link to the CDC study which includes links to all of the different RCTs. This push of fake science by the media is putting people at risk.
Well if you read the study then you would know that they only loose fitting surgical masks to be non effective. They did say that snug fitting n95 masks did a great job at protecting against flu virus. By the way this is not a flu virus and that study was not for the current pandemic. At least that’s what I read from your link. Wear a mask Karen!!!
Here comes all the non medical Drs telling us fast masks doesn’t work. Thats for your professional viewpoints.
Here’s the science. How about you actually read it for yourself instead of parroting whatever the TV tells you. It’s called being informed. Try it, you might like it.
So let’s be serious the experts already said early on that masks are essentially useless period there is effective at stopping a virus as a chain leak fence is stopping mosquitoes. But even if the masks were effective, the vast majority of people don’t wear them correctly. And even if they wore them correctly even more don’t handle them correctly. Masks are for all intents and purposes 100% useless.
No matter what is done, this virus will just have to run its course. Flattening the curve, masking up etc. all delays the inevitable. There is nothing that will prevent the spread of Covid.
As for the comment above stating that some people don’t wear masks just to support the President… who the heck said anything about showing support for the President!! That’s what it always comes down to, politics. The “what can you do for me” group against “ the what do I need to do” group.
Delay until the vaccine or death…I’ll try the vaccine. How about you?
If you can smell anything through your mask, then it is not an effective filter against covid-19. An n95 will only slightly reduce yours and everybody else’s risk.
COVID 19 virus particle size is 0.06 microns to .14 microns. The N95 mask filters down to 0.3 microns. So, N95 masks block few, if any covid-19 virus particles
What a utterly stupid article. You talked about everything but which were the good fabrics. What was was the purpose if you are not going to inform the reader.
What about the fabrics infused with copper fiber combined with other material. I have some socks for sale.
Gotta love all the anti-intellectuals in the comments, especially the ones posting links to old studies whose results they haven’t even come close to interpreting correctly. Wear a mask, people. Most old studies and every bit of new science (and there’s a lot, considering there’s never been such a large sample size to study) speak of the efficacy of wearing one (and wearing one properly), not only to prevent you from spreading the virus but also you from potentially getting it. You’re fighting against a wave of evidence with a pitchfork, all in an effort to prove you’re right about something. Shift the focus instead to potentially saving a life at any cost and you’ll realize there’s no downside to wearing a mask, even if the chance of you saving someone by wearing one were actually small.
As usual, the antimaskers misinterpret the science by confusing observations with findings. BTW, N95s filter particles smaller than .3 microns due to their electrostatic layer and Brownian Motion
I wanted to buy n95 mask for my Grandpa who has been facing severe chronic brochitis issues lately. Just wanted to know as to which type of adult diaper would be most effective for him to breathe easily.
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