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!
@windrunner @cstross they're not really the same thing - pm2.5 is particulate matter between 1 and 3 microns. MERV is an efficacy rating that incorporates the amounts of pm10, pm2.5, and pm1 removed from air.
MERV 13 for example has to catch 90% of pm10, 85% of pm2.5, and 50% of pm1.
@acb @cstross There's some positive early results!
BUT, and this is a great big BUT, do please stop thinking of single solutions. Survivability Onion needs multiple layers; policy failure after policy failure with SARS-CoV-2 has a root cause of "this one thing will fix it".
We need to apply all the things, and keep them applied.
This isn't the last plague.
@acb @cstross I know. I was excited about UV air cleaning as well. LED technology means photons are cheap now, right? (You know where this is headed by now …)
The kind of (high-energy photons) UVC which is effective at neutralizing viral particles is a bit … inconvenient. You can’t just use cheap UV LED technology, for instance: most of the efficient LEDs can only emit lower-energy UVB and UVA.
This means the best / most efficient light sources for UVC are generally vapor-arc lamps, with all the high voltage, glass tubes, and toxic fillings those imply. Plus, arc lamps have a limited service life - like measured in a few thousands of hours - which adds further complications to installing them in ventilation ducts.
So, redux: Powering an arc lamp is less efficient, hotter, and more physically hazardous than powering an LED. And UVC LED tech is still very much not mass-market-ready yet.
Far UVC is a different wavelength than traditional germicidal UV. 222nm is safe for humans, but lethal to coronaviruses.
A direct approach to limit airborne viral transmissions is to inactivate them within a short time of their production. Germicidal ultraviolet light, typically at 254 nm, is effective in this context but, used directly, can be a health hazard to skin and eyes. By contrast, far-UVC light (207–222 nm) efficiently kills pathogens potentially without harm to exposed human tissues. We previously demonstrated that 222-nm far-UVC light efficiently kills airborne influenza virus and we extend those studies to explore far-UVC efficacy against airborne human coronaviruses alpha HCoV-229E and beta HCoV-OC43. Low doses of 1.7 and 1.2 mJ/cm2 inactivated 99.9% of aerosolized coronavirus 229E and OC43, respectively. As all human coronaviruses have similar genomic sizes, far-UVC light would be expected to show similar inactivation efficiency against other human coronaviruses including SARS-CoV-2. Based on the beta-HCoV-OC43 results, continuous far-UVC exposure in occupied public locations at the current regulatory exposure limit (~3 mJ/cm2/hour) would result in ~90% viral inactivation in ~8 minutes, 95% in ~11 minutes, 99% in ~16 minutes and 99.9% inactivation in ~25 minutes. Thus while staying within current regulatory dose limits, low-dose-rate far-UVC exposure can potentially safely provide a major reduction in the ambient level of airborne coronaviruses in occupied public locations.
@snerkrabbledauber @cstross HEPA filters absolutely do block SARS-CoV-2 transmission.
"Airborne precautions" is the traditional term of art. It works. I'd be cranking up the rate of air changes per hour, but people are developing careful factual standards for this.
Every time you catch COVID, your brain shrinks, your immune system gets dysregulated, your cells get aged, and you suffer vascular assault. The assumption of indefinite survivability is intensely questionable.
@snerkrabbledauber
Please listen to anyone whose PhD thesis deals with the behavior of aerosols—or anyone who specializes in the study or treatment of aerosol-borne viruses.
They have been vocally advocating the use of MERV-13 filters, improved ventilation, and N95-or-better pretty much since the start of the pandemic.
They have been largely ignored, although that is finally starting to change (e.g. u.s. federal building requirements now require the use of MERV-13 filters.)
@GeoWend @bohemiancoast @hammancheez @cstross
"entitled übertwit" is snappier.
@davidfetter
Sadly, I feel it would bring in the hatred of the 70s... which weakens its use today.
Though it does get me thinking of calling them Uptight Geese?
@mfinch And the relics of the 1918-22 flu pandemic are with us today in the legacy of heaters/radiators bolted to walls beneath windows that open—it's wasteful b/c glass is a poor insulator, BUT it allows ventilation while preventing cold drafts—fresh air was considered necessary during the flu pandemic (it helps) and cold climates need heat, so you warm the air as it's drawn in.
We can do better today, but the past holds lessons.
@mfinch @cstross This happened in NZ. Houses that were not airtight and had an open fire did not have mould issues as the fire drew in air constantly.
Once things got sealed up indoor humidity starts to be a major issue so there is a big push to remember to manually ventilate and control moisture sources as well as finished heating properly.
@cstross @jdaviescoates on the very remote chance anyone here has the ability to influence such places, a company I know that sets this up and does the air quality monitoring is https://www.futuredecisions.net/covidcontrol.html
My guess is that no one ever wants their building occupants to ever know the actual ventilation / filteration levels of their buildings, tho.
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.
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