Daniel Bircher
Thanks for the interesting article. It would be helpful to link the mask samples (w numbers) to the graph with droplet count for easier reference. Thanks
20,014,574 infected, 734,755 dead, and only NOW we see the first basic study into whether or not masks work, with the researchers themselves saying "lot more work is needed to understand what kinds of masks are optimal" ???

No wonder it's so bad - the entirety of humanity, and especially everyone in charge, are all total morons. Not that we didn't know that from the beginning I guess...
1, ‘Surgical’ * Surgical mask, 3-layer
2, ‘Valved N95’ N95 mask with exhalation valve
3, ‘Knitted’ Knitted mask
4, ‘PolyProp’ 2-layer polypropylene apron mask
5, ‘Poly/Cotton’ Cotton-polypropylene-cotton mask
6, ‘MaxAT’ 1-layer Maxima AT mask
7, ‘Cotton2’ 2-layer cotton, pleated style mask
8, ‘Cotton4’ 2-layer cotton, Olson style mask
9, ‘Cotton3′ 2-layer cotton, pleated style mask
10, ‘Cotton1’ 1-layer cotton, pleated style mask
11, ‘Fleece’ Gaiter type neck fleece
12, ‘Bandana’ * Double-layer bandana
13, ‘Cotton5′ * 2-layer cotton, pleated style mask
14, ‘Fitted N95’ N95 mask, no exhalation valve, fitted
‘Swath’ Swath of mask material, polypropylene
‘None’ * Control experiment, no mask
Brian M
No surprises here, just begs more questions to be answered about the use of non-tested/standard face masks.
Is there a risk of building up an infectious dose (either direction)? Does it reduce social distancing due to over confidence in their use. Do re-used mask/discarded mask pose a risk.

With all this 'great hygiene' practice are we at risk of losing the ability to build up immunity to other virus/pathogens as a herd?
I recall reading that a mask made from an old cotton t-shirt was effective due to the tightness of the weave.
Laurent Coquilleau
The data shows that MOST mask covering have a significant impact in the number of emitted droplets. ONLY 1 out of 14 is worse than no covering. And this is the one you decided to highlight in your bold comment: "The notion that 'anything is better than nothing' didn't hold true".

Even if this is not false, Cherry picking is not science.

So let me summarize the true results of the study:
* Out of 14 different mask coverings, 12 SHOW A REDUCTION OF DROPLETS BY AT LEAST A FACTOR OF 3 !
* A simple bandana reduces the number of droplets by a factor of 2 !

Just do not wear a neck fleece. Because this material has a tendency to breakdown large droplets in smaller ones and let them go through, this is the ONLY tested face covering that is worse than wearing nothing.

Your interpretation of the data is intellectually wrong and socially irresponsible.
The only reason I wear a mask is to avoid making others uncomfortable. Washing your hands and using sanitizers is the way to go. And if possible, avoid touching door handles and other common things in public places.
You know, I've read studies of the efficacy of masks here in the USA since mid-March, but no one has really looked at the total viral load of a mask worn for several hours along with all these studies comparing mask materials one to another. Having had to purchase filtration systems in the past, I've always wondered about depth filters and their accumulated filtrate on the continued product stream. An example - I have a carbon filtration system at home for drinking water. It is supposed to be good for more than 1000 gallons (around 4000 liters), and I don't have a flow meter on my tap. So if I am drinking water at the 4250 liter point, how filtered is my water? Well if I am teaching a class for 8 hours wearing a mask, I may be collecting a good amount of my own aerosolized particulate matter, but how much of it stays with my mask, how long should I wear the mask before my constant breathing through it starts pushing the collected aerosolized material out the other side? Rather esoteric question given that we know masks reduce aerosolized spread in hospitals, and with highly infectious pulmonary diseases the properly fitted N95 is the standard of care. When in surgery, I generally change my mask each time I leave the operating room and put a fresh one on before the next procedure. When in the ICU I usually keep a mask around my neck and wear it properly when approaching a vulnerable or contagious patient. And I NEVER wear an N95 with an exhalational vent - those are for healthy workers in an environment like coal mining or sand blasting. Heck, they should use the complete "space suit" battery powered ventilation systems in those settings but they do cost money to obtain and maintain.
Your headline will encourage the crazed anti-maskers out there. Way to go! /s
Sow the seeds of doubt!