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Real-world data show that filters clean Covid-causing virus from air

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Re: Real-world data show that filters clean Covid-causing virus from air

#91

Post by clairity »

Wowfunhappy wrote: post #35
auslegung wrote: post #20

Earlier quoted context omitted.

I have believed this for about a year, based on things I was reading at that time. I thought this was widely known because as you point out, that’s kinda their purpose. This article acknowledges that it was shown to be effective in lab settings and this is mainly about seeing those results in real life settings. But come on, if anyone finds something that’s probably effective based on science and isn’t going to negat…

I'm student teaching in a third grade classroom, and I want to add a least a small counter: We are required to have two HEPA filters always running in the classroom. They are loud. Combined with the fact that (1) children mumble, (2) the children have masks on, and (3) everyone is supposed to stay 3+ feet apart, it's quite hard to hear what a lot of kids are saying! I don't know what the right answer is, but what we…

using air purifiers like that for corona is mostly theater anyway, since air purifiers don't filter the air evenly (despite the misnomer metric "air changes per hour") in a room. mostly, it filters really well near the purifiers and poorly everywhere else. this of course depends on the strength of the fan, but for most consumer air purifiers, it's likely a few feet radius at best. that's not to say that even that isn't worth having in an average bedroom, but in a classroom, it's likely not doing much at all.

also, you're already distancing (which is doing nearly all the work there) and wearing masks (which is mostly theater in a distanced classroom as well). the virus isn't free-floating live in the classroom. most virus falls to the ground directly. of what's aloft, it becomes inactivated pretty quickly for all sorts of reasons (dessication, ph, temperature, radiation, etc.) and most likely won't land anywhere near a viable infection spot. so almost no active virus is filtered out before it has a chance to reach a moist, viable passageway in another person.

even huge central commercial systems likely wouldn't filter out coronavirus before they die off or land somewhere harmlessly. it's another potential intervention that sounds plausible on the surface, but is mostly useless against covid.

Re: Real-world data show that filters clean Covid-causing virus from air

#92

Post by geoduck14 »

dragontamer wrote: post #19
throwaway984393 wrote: post #15

You can build your own high-flow HEPA filter for about $45: 1x 20-inch box fan ($20) 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) 1x roll of duct tape ($2.50) Air particle meters and other testing show they work just as well as big expensive machines (it's just the filter doing all the work). This is indeed a dirt cheap way to improve overall health.

> 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) That's a MERV-13 filter, not a HEPA filter. HEPA filters 99%+ of small (0.3um) particles per pass. A MERV-13 filter only filters like 60% per pass IIRC. That means that a 1000 cu. feet of air through the HEPA filter will result in 990+ cu. feet of clean air. While the MERV-13 filter will only produce 600 cu. feet of clean air. -------- A MERV13 filter would be good…

This is fascinating! If MERV 13 filters 60% with each pass, can we put 9 in a room to increase the circulation/filtration and eventually get to 99.7% filtration? Does it even work like this?

Also, I found this article which I found informative. Judge it as you please:

https://www.iso-aire.com/blog/what-are-the-differences-betwe...

Re: Real-world data show that filters clean Covid-causing virus from air

#93

Post by clairity »

makomk wrote: post #43
overton wrote: post #36

Earlier quoted context omitted.

Early on in the pandemic, the Canadian IPAC (Infection Control and Prevention) establishment came down hard against theories of airborne COVID transmission, at first even going so far as to not recommend masking. Even now that the science of airborne transmission has been established, they're waging a rearguard battle to obfuscate/deny it and airborne protections such as better ventilation and masking. If you go to a…

Airborne transmission and the usefulness of filters still doesn't seem that clearly established - this study didn't find that much virus in the air even without the filters, and most of the real-world transmission seems to involve people who were directly exposed to virus particles before they even had a chance to go through a filter, via standing next to someone or directly in an airflow path coming from their direc…

thanks for pointing this out. it gets lost in the fervor of trying to "fight the virus". most of our interventions are useless, and yet, we still insist on doing them. the virus just isn't aloft and active for very long. that's why the most dangerous activity is close conversation, something we tend to do around people we know well (friends & family), not strangers in public.

Re: Real-world data show that filters clean Covid-causing virus from air

#94

Post by roughly »

seventytwo wrote: post #80
roughly wrote: post #25

Earlier quoted context omitted.

With the added bonus that it would be better for the students’ health generally and would likely improve overall educational outcomes. An awful lot of our handling of COVID has been farcical (a year and a half in, we’re still relying on cloth masks and obsessively sanitizing surfaces), but in the case of schools it’s veered toward absurdist/tragic.

The authorities have long since stopped recommending cloth masks and surface cleaning. Anyone still applying or recommending those methods isn’t up to date. There’s nothing farcical about recommending cloth masks and surface cleaning during the first few months of the pandemic when nothing was known about how the virus spread and when masks needed to be reserved for those on the front lines. The only farcical piece i…

> Anyone still applying or recommending those methods isn’t up to date.

That's why it's farcical. In my area, you're required to wear your mask when you enter a restaurant and keep it on until you reach your table. Employees spend 8 hours breathing in the building through a cloth mask. Many places are still serving using single-use dishware to "stop the spread". Many people are still walking around with gloves on.

I'm not saying these were bad recommendations at the time, but they've turned into talismans and rituals we do to ward off the evil spirit of COVID while people broadly go about their lives as before.

Meanwhile, things like updating and repairing HVAC systems or restructuring buildings to maximize airflow, which both actually address COVID and have actual positive effects on health and wellbeing get short shrift, because we're wearing masks, so we're safe, and doing real work is expensive.

Re: Real-world data show that filters clean Covid-causing virus from air

#95

Post by jleyank »

trutannus wrote: post #84
jleyank wrote: post #72

Earlier quoted context omitted.

Have you lived any length of time in Canada? If so, where? While I have been fortunate enough to not have needed to go to hospital, my dental office reopened after the initial lockdown last year with a HEPA filter, doorway screen and other paraphernalia which made each workarea look like a clean room. And they shifted from water to air-driven cleaning and dressed like sci-fi actors. I would imagine the hospitals were…

> Have you lived any length of time in Canada? Yes, I am a Canadian. I lived there for 25 years. I have Canadian citizenship. Most of my family still lives there. I also ended up stuck in Ontario for most of COVID. I have family in Ontario, in Quebec, and elsewhere in the country. I don't think Ontario had a very good handle on COVID. It's also no secret that Canada is suffering a major staffing, and funding shortage…

The masks might have been after seeing a different comment, sorry. The problem with improving the system is that 1/3 of the country seems to want the US system in healthcare and probably (lots?) of other things. So it goes. Re: Ontario, I was looking at Ottawa specifically, the province generally and while it's "blessed" with a Conservative premier he's taken more medical advice (or indulged his populist leanings) more than other such premiers. Canadians, for the most part, are willing to play along which also helps.

Re: Real-world data show that filters clean Covid-causing virus from air

#96

Post by jph00 »

dragontamer wrote: post #19
throwaway984393 wrote: post #15

You can build your own high-flow HEPA filter for about $45: 1x 20-inch box fan ($20) 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) 1x roll of duct tape ($2.50) Air particle meters and other testing show they work just as well as big expensive machines (it's just the filter doing all the work). This is indeed a dirt cheap way to improve overall health.

> 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) That's a MERV-13 filter, not a HEPA filter. HEPA filters 99%+ of small (0.3um) particles per pass. A MERV-13 filter only filters like 60% per pass IIRC. That means that a 1000 cu. feet of air through the HEPA filter will result in 990+ cu. feet of clean air. While the MERV-13 filter will only produce 600 cu. feet of clean air. -------- A MERV13 filter would be good…

Thanks to a higher CADR, it can actually be better than HEPA in practice, if you use 4 filters to create a corsi-rosenthal box, as shown here:

https://www.texairfilters.com/its-all-about-the-air-flow-thr...

Re: Real-world data show that filters clean Covid-causing virus from air

#97

Post by Gibbon1 »

nostrebored wrote: post #75
Gibbon1 wrote: post #68

Earlier quoted context omitted.

We have the Austin Air Healhmates at work. They are quiet. That said the real failure was the FDA not making getting the vaccine approved for your 3rd graders by the start of the school year. Frankly I don't know how those guys can look themselves in the mirror while they are shaving in the morning. I think vaccine approval for 5-11 year olds is coming in early November.

Risk/reward here is absurd. This has never been about the safety of the children.

Ending the pandemic is totally in the interest of the children.

Re: Real-world data show that filters clean Covid-causing virus from air

#98

Post by nostrebored »

Gibbon1 wrote: post #97
nostrebored wrote: post #75

Earlier quoted context omitted.

Risk/reward here is absurd. This has never been about the safety of the children.

Ending the pandemic is totally in the interest of the children.

Aside from extremely poor studies about long covid in kids: why?

Re: Real-world data show that filters clean Covid-causing virus from air

#99

Post by clairity »

dragontamer wrote: post #19
throwaway984393 wrote: post #15

You can build your own high-flow HEPA filter for about $45: 1x 20-inch box fan ($20) 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) 1x roll of duct tape ($2.50) Air particle meters and other testing show they work just as well as big expensive machines (it's just the filter doing all the work). This is indeed a dirt cheap way to improve overall health.

> 1x 20x20 MERV-13+ MPR-2400+ HVAC air filter ($20) That's a MERV-13 filter, not a HEPA filter. HEPA filters 99%+ of small (0.3um) particles per pass. A MERV-13 filter only filters like 60% per pass IIRC. That means that a 1000 cu. feet of air through the HEPA filter will result in 990+ cu. feet of clean air. While the MERV-13 filter will only produce 600 cu. feet of clean air. -------- A MERV13 filter would be good…

note that phrase like "600ft³ of clean air" are misleading. filtration drops off rapidly with distance from the air purifier, so the fan would need to be quite oversized for a room to experience relatively even filtration. for most rooms, that wouldn't be comfortable, for both noise and draft reasons.

i'm down with air purifiers for indoor particulate matter (i.e., air pollution), but they're not really going to make a dent in covid transmission rates. transmission happens mainly during long face-to-face conversations, which mostly precedes/bypasses room air filtration.

Re: Real-world data show that filters clean Covid-causing virus from air

#100

Post by Gibbon1 »

nostrebored wrote: post #98
Gibbon1 wrote: post #97

Earlier quoted context omitted.

Ending the pandemic is totally in the interest of the children.

Aside from extremely poor studies about long covid in kids: why?

In the US about 120,000 children lost a primary care giver to covid. Is you are sane that counts for something.
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