Video compares droplet sprays when wearing different masks -- and no mask at all

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Yet there are those who will refuse to wear a mask.
Wear you mask. It isn’t for you it is for your parents/grandparents or someone elses parents/grandparents or worse kids.



I’m always baffled by the common anti-masker question: “Do you think that mask will protect you?”

No. No I do not. I think this mask will help protect you. I wish you would wear a mask to help protect me.

Either that reality is lost on them, or their question is lost on me, and it’s meant more as a rhetorical threat. :worried:



There’s evidence that wearing a mask helps reduce the severity of COVID-19 should you get infected. Wearing a mask in public protects everyone.


I’d find this more interesting if it showed a second top view that visualized droplet escape from the sides of the masks.

It would also be interesting to see (if possible) visualization by droplet size.

A professional parallel for me is acoustic fabrics. A blanket rating has little useful information, a rating broken down by frequency (typical 1/3 octave bands) is useful.

All that said I’m not disputing masking. My wife is a physician (OB/GYN) who has been treating covid positive patients since her hospital started testing patients (and realistically probably before that). Through the use of double masking and a face shield we have (to the best of our knowledge) not caught covid. She largely is not using a N95 even with covid patients.


Important to note that, in a medical setting especially, N95’s protect the wearer, surgical masks/face coverings protect everybody else. There will be exhaust from the sides, but at lower velocity. Perfect? No. Effective? Absolutely.


The take-away from that is that even wearing a mask, we should still sneeze into our elbows.


Here’s a more scientific and rigorous analysis.


Curious—this seems counterintuitive to me—an N95 seems like it would trap particles going in either direction equally well. How does it fail to trap them on the way out?

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Most N95’s have a flapper valve on them to make exhalation easier, and to protect the seal to your face. The effect is that exhaled air is unfiltered, while inhaled air is.


I was definitely surprised at how close he had to get for the mask to fail, very fun video :slight_smile:


I really wish that I could find better info comparing different washable cloth masks, looking at different brands. The fabrics and styles vary a lot, and probably that impacts their effectiveness. Given that we’re all wearing these every day, I don’t want to use disposables. But it’s hard to know which washable one is “best.”


Not all N95 respirators have exhalation valves. Masks with exhalation valves can’t be used in sterile fields and the CDC recommends against them for source control (preventing droplet spray.) If you have to wear a mask with an exhalation valve it’s recommended that you tape them shut.


Its really bizarre to watch. Its like the idea of wearing a mask to protect someone else just does not compute. Some people just can’t handle that mental state and immediately revert to “it must be to protect yourself and your family”.

True, although that is fairly new data and still subject to more uncertainty. It also seems likely that a lot of the efficacy at protecting the wearer depends how careful you are: how well does the mask fit, the material the mask is made from, and possibly whether you avoid touching the mask and wash your hands when taking it on and off (I say possibly since we still have very little evidence for or against fomite mediated transmission). On the other hand, even a poorly fit mask made of loose knit tee shirt fabric worn with no other precautions seems to reduce the amount of virus you spew all over the place and how far it travels.


Well, there are two kinds. Industrial and woodworking dust masks usually have a valve to make breathing easier. Medical respirators usually either have no valve or the have a valve with a relatively high opening pressure. The purpose is that normal breathing goes through the mask but strong/sudden exhalation that would be strong enough to lift the mask off your face will instead be directed out the valve, usually facing down.


Cynically, I’d say they don’t understand because they don’t want to understand. They see a benefit to not getting it (the convenience of not wearing a mask) so they have an incentive to keep on not getting it.

Less cynically, my own experience giving advice as part of my job (but NOT in the medical context, to be clear) is that some people just cannot process risk except in absolutes. I get asked all the time “Do I have to do X?”. The answer is rarely a straighforward yes, it’s usually more “Doing X avoids your risk of bad thing Y happening, but there are a number of other things you should also do to reduce the risk of Bad Thing Y happening. Even if you do all those things, Bad Thing Y might still happen, but you will have reduced your risk. But Bad Thing Y is not guaranteed to happen, so even if you don’t do anything, Bad Thing Y might not happen anyway”.

But if I said that, I’d get blank stares and then: “OK…so do I have to do X?”

So I just say “Yes”.


Rule 34.

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My own uncharitible explanation is that it is toxic individualism that we Americans pride ourselves on so much. “I’m responsible for myself, everyone else needs to be responsible for themselves” – an attitude that is just completely unacceptable when it comes to public health.

Yes, I agree a big part of it is that people just don’t understand that an epidemic is a statistical problem of risk reduction. The CDCs primary goal isn’t really to protect you or keep you from getting sick. It is to keep everybody from getting sick. I was talking to my mom the other day about an eposode of This week in virology ( where the guest talked about how we should be focusing on tests that are fast and cheap even at the expense of sensitivity, and that PCR makes a very good clinical test (where the point is to inform treatment of sick people) but as used currently makes a poor screening test used to stop the spread of an epidemic. According to him some tests that are only “50%” accurate (there is a fair bit of detail on what that 50% means) would be just as good for screening, and much better if they were faster or could be done in higher volume due to lower cost. It was really hard for my mom to accept, she was fixated on “but the test could say I am not sick when I am” My mom does accounting research. She knows quantitative thinking, she knows statistics. But when it comes to her health it took a bit for her to accept that a less accurate test could have better outcomes for everyone, even herself – because the point is that if we can stop the spread then far fewer people will get sick.