Reminder, folks: the COVID19 pandemic is NOT over, it's just that the big commercial landlords decided it was hurting their business rents so leaned hard on the politicians and media to SAY that it's over.
Right now China is in the FO phase of FAFO, and involuntarily providing an amplifier for a new extra-virulent strain that'll make an end run around our half-assed vaccines AGAIN.
Stay safe in 2023!
But DO we need them? There was a wildly cited paper recommending HEPA filters, but this was based on lab results, ie, theoretical.
Here in #Ontario, the province promised all school rooms would have a filtre, but my repeated asking if this was done was never answered. One teacher did confirm their school had them, but I'm unable to find any follow up studies to see if these had any measurable impact.
Do you know of any such studies?
@teledyn @cstross @pluralistic "A MERV 13 filter must remove at least 50% of particles between 0.3 and 1 μm, 85% from 1 – 3 μm and 90% from 3 – 10 μm."
By ANSI/ASHRAE standard
"The virus is 0.1 μm (micrometers), but it is NOT naked in the air. The typical respiratory aerosol that contains viruses and is generated when talking is ~3 μm.
And in any case all filters work well at 0.1 μm, because brownian motion helps a lot for filters to capture small aerosol."
Most anything you'd like to know about this can be found here:
https://docs.google.com/document/d/1fB5pysccOHvxphpTmCG_TGdytavMmc1cUumn8m0pwzo/edit
Written by a great group of professors.
FAQs on Protecting Yourself from COVID-19 Aerosol Transmission Shortcut to this page: https://tinyurl.com/FAQ-aerosols Version: 1.88, 13-Aug-2021 Click here to jump over the scientific & historical details and go straight to the recommendations, Click here for automatic translation into many l...
The only part I'm (still) looking for is "Did it work?" 😏
Specifically in schools, but any will do.
@cstross @pluralistic @teledyn
Ok, so clearly I’m misunderstanding you then. Of course it filters out viruses. That’s not, scientifically speaking, a question. It’s just physics.
“HEPA filters are no less than 99.97% efficient at capturing human-generated viral particles associated with SARS-CoV-2.” - The CDC
I'm not sure how to be more clear. I have no doubts the specs of the machine, but when deployed it is not on lab conditions, it is in a institutional space, and as we all know, theory and practice are different things.
It would seem a simple matter, especially as these, if they were given to all schools, were not deployed at the same time. So was it 5% of a solution, 45%, 0.05%...
But clearly you don't much care, so I'll drop it and keep looking for the followup.
@pluralistic @teledyn @cstross
I’m not going to lie, I’m trying to understand what you’re asking and I’m still not getting it. Not trying to be obtuse.
I think what you’re asking for is a case study in a school? That would be unethical to set up the way you want, if I’m understanding. You’d give some schools/classrooms HEPA filters, others none, send in sick people and see how many kids got sick in each case?
It’s not something that needs to be done. They suck in air and filter it. You can measure what goes in, how much airflow, and what goes out after filtration. Measure your room and decide how many air changes per amount of time you want in the room. It’s nothing new. Every air conditioner has filters and stand-alone HEPA filters have been around for 75 years.
I’m sorry if I’m still not getting you. Feel free to move on without further discussion if you’d like.
@teledyn @cstross @pluralistic
Here's hospital data:
https://www.medrxiv.org/content/10.1101/2021.09.16.21263684v1
But you're not going to find the type of "real world" study I believe you're looking for. It's just not ethical to infect a control group of kids.
I believe I mentioned that filtres were not rolled out instantaneously, thus control groups. This is, in fact, how mask effacy was confirmed. No privacy risks.
But privacy raises another curio. Here in Ontario we were not given local "heat maps" during the pandemic because, they say, our density is so small, one could figure out individuals from the aggregate stat. Thus the maps put a big dot over Hearst, as if the risk was the same whether Toronto or Gravenhurst.
Charlie Stross
teledyn 𓂀
A Concerned Scientist