I got a few questions on that thread about particles floating. Here's a quick explainer although of course there are plenty of air experts on here as well, so I will try to do a with a lot of pictures to be different.
Historically, humanity has had two major theories of disease spread: miasma (arises in swamps and floats in air) and contagionism (disease spread by contact between people).
In the 1800s we learned about germs, and that they live in us, and that we spread them.
In 1912 a guy named Chapin wrote a book that examined spread of disease. He thought it was spread by droplets.
He thought so because 1. most spread was at close distance 2. he thought things stuck to water and don’t get thrown off it, 3. they could not culture bacteria well at the time and 4. he thought that if you told people disease was in the air they would act like dirty animals.
But to him, remember, droplets meant “not airborne” and “airborne” meant floated over great distances.
Even though later scientists like Wells and Wells wrote articles debunking this such as this one in 1936 explaining why everything floated in small particles in the air, the more prominent scientists believed Chapin and continued to push his work.
Part of the problem was “airborne” didn’t have a great definition. it just meant “we saw it transmit more than 1 or 2m or so”
And part of the problem became we then connected “airborne” to providing workers N95s, because if virus spread via droplets that fall to ground, a surgical mask is good enough
No. They all transmit via floating aerosols. Some just more infectious so we see spread at longer range
So, as we entered this pandemic, the predominant thinking was disease is spread by larger droplets that fall to the ground in 1m, 1.5m, or 2m. They either land in our eyes (etc) or on a surface and we touch it.
Even though this theory is full of holes, even per the @WHO’s writings.
Disease spreads in the small particles in the air, called aerosols. An “aerosol” is technically a suspension of fine particles in air (or another gas) of any size.
Because of droplet theory, we’ve come to believe virus is transmitted in droplets that fall to the ground relatively quickly (few seconds).
In fact, they float for hours.
Older ref says:
A 0.1um particle floats practically forever. It settles at a rate of .007 feet per minute.
A 10um particle settles at .59 feet per minute.
And we need the WHO to change to acknowledge this because their guidance trickles down to national groups, and means healthcare are not getting N95s to protect against these smaller particles
@jljcolorado A more fulsome history is in our preprint here, with a collection of people who have been yelling this stuff for ages, most of them air experts in that list of experts.
And of course this thread (whipped up quickly) is in no way complete.
I left out tons of references, such as this one about knowledge from the 1700s about ventilation slashing transmission rates.
Miasma was wrong, but its cures were in part right
And here is the ramifications of "droplet" which is 6 feet and 15 minutes were always made up nonsense. Sure you can use them as cutoffs for contact tracing, but they're meaningless
And @kprather88 saying, yet again, that aerosols float
Maybe medical officers of health (MOHs) need to be reminded of what the Ontario Medical Association thinks their role is:
"Guarding the Health of Citizens".
Hmm.
And all I'm doing is clearing out old PDFs. Imagine I started making a case for their abdication of their duty?
It's almost comical
This report is entertaining to me because it's the OMA lobbying for more jobs. They encouraged the maintenance of all the local community boards and that there needed to be an MOH (who are very well paid) in each one. The opposite of what SARS Commission said was needed.