Study: Air purifier use at daycare centres cut kids' sick days by a third (2023)

[PaulKeeble]

There has been a number of these studies in schools and hospitals showing HEPA filters reduce up to about 2/3rd of infections. We now know many viruses are airborne including Covid and Al Hubbard's studies on how long virus is viable has shown it can be hours and it's helped by high CO2. Air circulation and reducing CO2 makes a big difference as well.

[lolinder]

Do we have evidence that CO2 is causal or is it still just a correlation? In general, poor ventilation + humans = high CO2, so unless there was a controlled experiment done that's a pretty strong confounding factor.

[dzhiurgis]

Do you still need HEPA/air purifier if you have decent ERV/HRV?

[retrochameleon]

https://youtu.be/gaQTYrisieA

This is an extremely well researched and presented video that exposes the fact that HEPA purifier marketing is a bit of a scam. The most important factor in air purifiers is not the filter but Clean Air Delivery Rate. You can only make a difference if you are moving air through the filters faster than particulate is introduced into the air.

I just returned a Medify filter because their advertised square footage is way higher than what the purifier should support based on the info in the video; it is inadequate. No idea how they are calculating their numbers - not to mention it's probably at the max speed setting - but it doesn't align with the sources from the video.

On top of that, smaller air purifiers must move air faster, be noisier, and the smallest sizes of particulate are captured most effectively at low velocities.

Use something like this to make a nicer version of a CR box: https://acinfinity.com/component-cooling/cabinet-fan-systems...

Or buy one of these: https://www.cleanairkits.com/

Those seem to be the best options that ACTUALLY work.

[schiffern]

Yes, almost all websites give the filter "square footage" at a measly 1 air change per hour. So essentially they take the CADR, divide it by the (assumed) height of the room, and that's the square footage or square meters. Very flawed methodology!

Typically for respiratory pathogens you want to shoot for 6+ ACH, so as a very rough initial guess I often simply divide the rated area by 10.

And yes, every manufacturer only gives specs for the highest fan setting. This is misleading because typically this fan setting is very loud, so few people actually run it 24/7 (and those who do will probably suffer hearing loss).

[thinkcontext]

If borne out this is pretty big. A huge amount of productivity is lost by parents taking care of sick kids or who get sick from their kids. Further it might even lessen the overall spread of seasonal diseases.

[_dain_]

This is one of the three educational interventions with solid evidence of it working. The other two are air conditioning and free school lunches. People don't get excited over them though, because they have nothing to do with teachers or curriculum or educational theory.

[mmcloughlin]

Perhaps there is some evidence that people do get excited about free school lunches: Governor Tim Walz’s lunch policy in Minnesota has been a part of the buzz surrounding his recent Vice Presidential nomination.

https://www.cnbc.com/2024/08/19/universal-free-school-lunche...

[stevenwoo]

There's also the accidental study of air filters where the outside air quality was not that bad. study https://www.edworkingpapers.com/ai20-188 background https://wfis.org/installing-air-filters-in-classrooms-has-su...

[olalonde]

> free school lunches

What are you referring to?

[elric]

I installed a Zehnder ComfoAir Q ventilation system in my home. It has heat and moisture recuperation capabilities. It's currently refreshing the air at around 100m³/hour. It has an F7 (aka "ISO Fine" or "MERV 13") filter. Since installing it, my asthma has improved a fair bit, and I'm sneezing a lot less. Added benefit, virtually no mosquitoes have been able to enter my home. I'm still considering getting an extra filter addon to filter out more fine soot from car exhaust etc, but even without that option I've been very happy with the results.

Edit: hit reply too soon. Wanted to add: are air purifiers as effective as increased ventilation? Should we combine the two?

[amluto]

That Zehnder unit is fantastic. The filter, not so much. (“ISO Fine” is IMO particularly embarrassing. It should say something more like “ISO ePM 1 40%”, and then buyers would think “40%? that’s lousy!”). Even the fancier ComfoWell filter is crap. And they’re overpriced, have lots of resistance, and don’t last long. You can confirm how poorly it works with a portable particle counter.

Get something like this if you have space:

https://www.hvacquick.com/products/residential/Air-Filters/P...

And consider putting it upstream of the Zehnder unit in the outdoor intake duct. Then it will extend your ISO Fine filter’s lifetime to effectively infinity. Or you could replace it with ISO Coarse. Or with nothing :)

[dzhiurgis]

I've installed HRV myself too. I have a reasonably easy to access roof space, but for a large guy still took over half a day. Cost 1.5k NZD, but not mosquito free, it's warmer indoors plus when neighbours fire up their fireplaces I only get an occasional little whiff of it.

Best thing I did for my house so far!

[turtlebits]

Get an AQ monitor and a standalone filter, it will be able to constantly filter air vs the once during fresh air intake.

Also my ERV only runs on demand (~1/3 of the time, which is not enough filtration)

[plasticchris]

With my experience around poorer schools in the USA I would worry that the filter wouldn’t get replaced for decades and itself become a breeding ground for molds.

[erikvanoosten]

You don't need poor schools for that. Just ~3 years ago exactly this happened to a public primary school in a rich neighborhood of Haarlem (The Netherlands). If I remember correctly, the filters had not been replaced for 8 years.

[swagasaurus-rex]

There was a great deal of interest in how to remove airborne viruses during Covid.

One of the biggest takeaways seemed to be that UV light destroys viruses in seconds.

Seems like there a lot of things we could do

[LinuxBender]

Anecdotally can vouch for air purifiers. I bought an old earth bermed home. I suspected radon may be an issue. Purchased 2 AirThings and they were off the government charts so to confirm Radon Daughters were being produced I bought more air purifiers and an Alpha Geiger Counter. I can hold it 2 inches from any of my filters and the alarm sounds. 640 CPM alpha radiation. That changed my project priorities. The filters only bought me some time as the air away from the filters is the same level of radiation as outdoor background noise but obviously the source is still emitting gas. I will probably just bulldoze this place.

[ComputerGuru]

Radon mitigation systems work. And they’re cheap.

[chriscjcj]

Can anyone provide or link to some solid guidelines on what kind/brand of air purifiers actually do real effective filtration vs. garbage products? I have found that a great many of these "air purifiers" have great marketing and make amazing claims.

[bjoli]

4x merv 13 filters.

A fan.

Now you have yourself a high performing air purifier.

[sbochins]

I’ve been happy with Austin Air purifiers. Most of the other brands help, but don’t handle most VOCs. If you have allergies or other issues, it’s better to stick with top quality brands. https://housefresh.com/austin-air-healthmate/

[evilmusic]

Some good tips here https://youtu.be/nE3u-2EyW-s

[alliao]

cr box basically owns everything else go build a couple yourself, it's great, if you live in the US you can order kits too

[tiahura]

A 20” box fan and 4 20” furnace filters

[ClumsyPilot]

Basically all filters work l, they just need to be big enough. The largest air purifier from Xiaomi is okay, ones from ikea are a little small but nicely made

[encoderer]

Even better (where weather allows) is fully outdoor daycare. We were fortunate to have only the briefest of shut downs during COVID.

Obviously impractical in many areas but it's part of the California dividend

[kjkjadksj]

So long as you are far enough from a major freeway, major road, major airport, or major port. With those requirements the number of californian daycares or schools that meet that criteria shortens significantly.

[Rendello]

It was a big thing in the early 1900s too:

https://en.wikipedia.org/wiki/Open_air_school

[esafak]

And it's good for your eyesight.

[dzhiurgis]

Unless you don't want to expose your kids to sun screen, eeek /s

[switch007]

Good news. Hopefully a country as wealthy as Finland can just roll this out countrywide without much thought, if not already standard

[readthenotes1]

Without much thought? Without much thought I would say that the recent experience of preventing children from catching communicable diseases have shown it to be a devil's bargain and we would be wise to keep their immune systems constantly exercised

[taeric]

So from 10-13 down to 7-9? Nice.

Will be neat to see if the kids were still carriers, but managed to keep the viral loads down such that they weren't "sick" during that time. I recall a study a few years back that said kids at that age were basically always sick, just not often symptomatic.

[xyst]

Any HVAC professionals or plumbers know if a mini-split A/C system can be outfitted with UV bulbs?

Have a few Levoit air purifiers that sit flush against the wall. But would be nice to have an extra layer at the source.

[thedougd]

I would imagine it would destroy the plastic. A common problem with retrofitting stardard split systems. They require a UV resistant drain pans.

[abracadaniel]

REME Halo was recommended to me and I bought one. Hard to know if you’re making a difference, but it’s something.

[photochemsyn]

I wouldn't call this a statistically significant result, and the fact that the buildings in question had good mechanical air ventilation could very well explain the results:

> "Utilizing the model, we used portable air cleaners in two day care units (A and B, number of children participating in the study n = 43) and compared infection incidents between the two intervention units to the rest of the units in city of Helsinki (n = 607). The intervention buildings had mechanical supply and exhaust air ventilation."

https://www.sciencedirect.com/science/article/pii/S295036202...

You also have to consider external air quality, as ventilating a building with polluted air would have negative effects like increased asthma. In that case perhaps a sealed building with air purifiers is a better option, but then CO2 buildup is a concern, so you'd need CO2 scrubbers, which are expensive.

That's why clean air regulations matter, and getting off fossil fuel combustion as an energy source (and limiting pesticide/herbicide use in agricultural zones) is the easiest route forward.

[duxup]

Is there any information on the type / price of these air purifiers?

There's a lot of "air purifiers" out there on the market.

[PaulKeeble]

In a lot of tests Corsi Rosenthal boxes tend to outperform most commercial offerings and they are very cheap as they are a box fan duct taped to some MERV13 filters. Effectiveness is a lot about air exchanges an hour.

[amluto]

It would be awesome if they were IKEA purifiers. Cheap media and excellent CADR/W.

[rajnathani]

Given that air purifiers could increase airborne endotoxin levels [0], that instead better ventilation should be prioritized as it also solves the higher CO2 problem, where we know cognitive function slows down due to higher CO2 levels [1]. Given that OSHA sets an upper limit on CO2 in the workplace, I wonder whether daycare centers have such norms enforced too.

[0] https://www.sciencedirect.com/science/article/pii/S016041202...

[1] https://www.ucl.ac.uk/bartlett/energy/news/2018/dec/study-mi...

[throw7]

Indoor air environments are usually poor. Just having outside air from open windows would be an improvement.

[dzhiurgis]

Which easily excludes 80%+ of the places either due cold, heat or pollution.

[unglaublich]

Yes, please. My colleagues, who are parents, are constantly sick whenever their children are at daycare, and I have no interest in the constant coughing and/or getting sick myself.

[modeless]

Near UV seems really promising for preventing indoor disease transmission as well. Has there been any more research on it lately?

[amluto]

Do you mean far-UVC, around 222nm? It seemed like the major issues were the sources being expensive, the sources being from dubious vendors with no standard certification (I would be concerned that my “222nm” source might have a lot of inadvertent emission at other wavelengths), and possible damage over time to whatever you aim it at.

[emeril]

isn't UV light dangerous for people?

perhaps there's certain wavelengths that kill viruses/bacteria but don't increase cancer risk?

[Fire-Dragon-DoL]

This would he huge. Aside from the huge benefit, it would be great not having runny nose or cough 6 months of the year.