My work takes me into this field. A mask is a filter, albeit, a two way filter. It allows air to flow in while capturing particles it’s designed for.

I’m sure you’ve heard of the N95 mask. The N stands for  “not for oil aerosols”  meaning it’s intended for dry flows. Other masks are designed for higher moisture flows. The 95 stands for 95% particle capture efficiency on submicron particles.

The tee-shirt masks many of us wear vary in efficiency but unlikely to be greater than 25%.

When we exhale, we exhaust respiratory droplets and aerosols which are primarily moisture from our respiratory system. Contained within the droplets, are all manners of particles the force of the exiting air dragged along with it. If we have a respiratory illness, we spread these, that’s how we pass the flu, colds etc..

A mask reduces, not eliminates, the larger respiratory droplets, that’s why your mask gets damp. The larger droplets that escape your masks behave ballisticaly, which is to say they fall to nearby surfaces based on their initial velocity, size, humidity, other air conditions etc..

A high percentage of the  smaller aerosols pass through the masks and are buoyant enough to remain suspended where they can drift on air currents.
The same efficiency of a mask in stopping exhaling aerosols exist when inhaling.

So, all this means yes, wearing a masks reduces, doesn’t eliminate, the amount of droplets and aerosols an infected person expels. If you are outside the social distance zone, you are unlikely to inhale large droplets from that person. Aerosols however will pass through your masks. Again depends on your masks but assume 50%, could be more, could be less.

The $64000 question revolves around the infectious dose require to pass the infection. Diseases labeled as airborne require very few. Others require a high dose. This isn’t known yet and various tremendously based upon that person’s health anyway.

It’s interesting to note on a call this week with top medical providers, they reported they do extensive contact tracing for doctors and staff who test positive and the vast majority, report almost all positive cases were contracted outside the facility. The obvious reason is because inside, they wear N95 masks, have been trained how to ensure they fit properly, and they follow other guidelines such as regular washing etc..

There are not enough N95 masks to go around. If there were, infection rates in all areas would be closer to healthcare infection rates.

Bottom line is this. Think about droplets and aerosols like cigarette smoke. If you don’t like smoke, you move away until the smell is tolerable. If you’re in an enclosed space without a mask, imagine someone is smoking. If you’re close enough that the smoke would dominate the air you breathe, you’re probably close enough to inhale enough aerosols to risk an infection. If you’re outside and normal distance away from people, it’s probably a safe risk.

Inside in poorly ventilated areas is the highest risk. Your little tee shirt mask would do very little to protect you.

Bottom line is this. Think about droplets and aerosols like cigarette smoke. If you don’t like smoke, you move away until the smell is tolerable. If you’re in an enclosed space without a mask, imagine someone is smoking. If you’re close enough that the smoke would dominate the air you breathe, you’re probably close enough to inhale enough aerosols to risk an infection. If you’re outside and normal distance away from people, it’s probably a safe risk.


 This is a good way to look at it, except for things like the military doesn't tell soldiers to wear ponchos to stop bullets so staying away from people won't reduce my chances for infection.  That's the logic I get in response to your post.

  Overall though I think we are seeing the same things.  Masks aren't a solution, they are part of overall mitigation effort.  
 

Chemist46
I was trained as a chemist. A large part of my professional career was working in various parts of the filtration industry. I developed a line of mixed esters of cellulose membrane filters. Millipore type filters, that were used to sterilize flu vaccines for Merck Sharp and Dohme as well as other medical products companies. I developed respiratory protection products for Wilson Safety Products used in the mining industry. I worked for Baxter developing medical / IV filters. I have patents on three IV filters I invented. Baxter sold more than 5 million of one of those every year for most of a decade. I know a little bit about filters.
Surgical masks were not designed as filters and were not intended to be used as filters. Surgical masks were designed to be used by surgeons standing face down over an operating table holding a patient with an open wound. The surgeon wearing the mask would be able to talk to others in the room without discharging spittle droplets into the patient’s wound. Spittle droplets are large and can cause infection.
I witnessed a test of surgical masks. Small plaster particles were generated in a room. They were visible as a white dust in the air. A man was properly fitted with a surgical mask and spent a short time in the room. When he came out the mask was removed. A camera was focused on the man’s face. The entire area that had been covered by the mask was coated by the white dust. The camera showed that his nostrils and his mouth had been penetrated by the white dust. The dust particles were measured and found to be around 40 micrometers in diameter. The particles that penetrated the mask were the same diameter.
Covid-19 virus molecules are about 0.1 micrometers in diameter. That is 400 times smaller than the plaster particles that penetrated the mask.
Surgical masks will not prevent the wearer from inhaling or exhaling viruses or bacteria. They provide absolutely no protection for either the wearer or anyone nearby. They create a very dangerous false sense of security for everyone. They also force the wearer to rebreath carbon dioxide. Which will over time reduce the wearers blood oxygen level. That can become very dangerous especially for older people.
This farce is being promoted by sleazy politicians who believe that if they can convince people that they are protecting them or creating a safe environment for them by pushing this mask farce those people will re-elect them.
All politicians pushing this dangerous mask farce should be voted out of office as soon as possible.


https://www.theburningplatform.com/2020/09/20/belgian-medical-profession-dema...

Countries and states see increases in transmission... they enact mask and distancing rules, and transmission goes down.
Period...
It works... it works over and ever again.
There are no instances where masks and distancing have made transmission go up.

How do we possibly have disagreement here?...
It is asinine... It is Trumpist...

Eegore wrote on 09/18/20 at 20:33:58:

...   The mask is to reduce, and only reduce with the exemption of all other words, just reduce, the amount of fluid any breathing human expels into the atmosphere around them.  ...

And a Poncho, absolutely Reduces, the velocity of a bullet.

OH and,

Eegore wrote on 09/20/20 at 10:48:22:

   Masks are no to stop airborne particles from coming in.  
It's not about my breath going into your mouth.
 Masks are not, as in NOT, to stop airborne particles.
...  Stop pretending masks are to stop airborne particulates.  
They aren't.    

Just checking,
A Mask is to slow down the amount of great big 'things'.
(Which may or, may not, contain c-19)
Also a Mask, (98.97%) does not stop little things.
(Which may or may not contain c-19)
Then if a mask does not prevent little things from coming in,
it will not stop little things from going out ?

So then if someone is coughing, sneezing, runny nose,
and they wear a 'mask',
it is perfectly OK for them to go to the store ?
Perfectly OK to be around them,
(as long as they are wearing a mask)?

Or should they, STAY HOME ?
and 99.954% of the REST of the people,
go about their normal lives ?

justin_o_guy2 wrote on 09/20/20 at 12:46:59:

... Brainwashed gutless sheeple, ...

That one thing is the entire reason !

Now, (most people were not to sure in Jan/Feb)
But NOW, that the MAJORITY of people have learned the TRUTH.

From the land of, 'Rocks and Cows',
the vast, VAST majority of the MN,
" ...Brainwashed gutless sheeple..."
live in Mpls, and elected, Gov. Walz, AG Ellison, and lhan Abdullahi Omar.

The Anti American, AG Ellison is doing everything he can do to protect Walz. He had Blocked 2, well written, articles for recall of Walz.

Mpls & Dist 5 is going to do everything it can to rig, cheat, falsify, and ALLOW non Citizens to vote.
AND, vote multiple times !

"...Walz can be heard describing an election map of Minnesota. Walz references “all that red across there,” presumably referring to outstate Minnesota, calling the Republican-leaning area “mostly rocks and cows....”

Eegore wrote on 09/20/20 at 11:02:43:

...  When I was at the CO ICC looking over SARS-COV-2 lab positive cases from a single building we noticed that the business that required masks had fewer cases. ... 

Do you know, or did anybody research,
'the rest of the story, ?

Early on, everybody in MN was talking about a huge outbreak in 2 meat packing plants. And how they had to shut down.
Just Horrible, see the news at 5-6 & 10 for two weeks.

Someone did a little digging.
Discovered, cars going to and from work were Packed with workers.
The workers were Packed in multi generation houses.
The houses had less than stellar satiation conditions.
The workers also discovered if they stayed home,
(being 'sick' from c-19),
they received UN-employment, and a stipend from Stat/Fed.
Making more money sitting on the porch drinking Mint Julips,
than working.

Golly Gee Wally,
the, 'news' suddenly stopped 'reporting' on it !

So, being the analytical person you represent yourself to be.
Did you, or anyone else look at any other factors in the 'unknown' case you talk about ?