A review of the effects of installing air filters in classrooms | Hacker News Reader

A review of the effects of installing air filters in classrooms

statmodeling.stat.columbia.edu

90 pointsthatcat26 comments

A thread on the article that Gelman is responding to: https://news.ycombinator.com/item?id=22006033

> When you see a report of an interesting study, contact the authors and push them with hard questions: not just “Can you elaborate on the importance of this result?” but also “How might this result be criticized?”, “What’s the shakiest thing you’re claiming?”, “Who are the people who won’t be convinced by this paper?”, etc.

That's a nice set questions, unnervingly disarming! Versatile too - it would be interesting to see some journalists use a similar line of enquiry with pronouncers of political policy.

The sad fact is that sober analyses like these won't make their way around. Meaning a large subset of readers of the first article will have more "evidence" for their mistaken interventions to improve academic performance. On the plus side, installing air filters in schools is cheap enough that they should do it anyway -- not to mention the morality of forcing kids to be in school for half the day when the conditions aren't healthy.

It's obvious. The author of the air filter paper didn't have the luxury of having air filters in their office. They're hardly to blame.

I thought a current suspect of diminished classroom performance is CO2, and a typical filter won't help there. I'd like to see a study with CO2 sequestration in classrooms and/or other people-dense indoor settings.

> CO2 sequestration

Or perhaps design buildings with windows that people can open?

At the risk of sounding facetious, I think most people underestimate how much CO2 is produced by 20 odd people in a room. Equally we underestimate how much air is renewed by just opening a window.

I really wish this was a continuing series on research that gets picked up in the popular media. There's so much questionable coverage out there.

That is in fact a common topic on Gelman's blog, if you go through the (large) archive.

..or schools willing to change their air filters (or attempt to measure the effect of having changed their air filters) are more likely to be among the higher performers according to traditional KPIs (when controlled for observer bias)?

The article explains why the air filters were installed, and it doesn't fit your supposition.

agree, I actually expect there to be all sorts of positive correlations with clean air - but they all start with caring about it enough to do something like change a filter

gfody, the schools had no choice about changing their filter or not. In fact, the whole premise of the study relies upon that fact!

good point, crucial even.. thank you I should get back to work :)

New study finds no evidence of educational benefits from installing air filters in classrooms

A new study was performed of a set of Los Angeles schools and found no effects on test scores, comparing schools with and without newly-installed air filters.

However, this was a small study, and even though it found null effects, it could still be worth exploring the idea of installing air filters in classrooms, given all that we believe about the bad effects of air pollution.

We should not let this particular null study deter us from continuing to explore this possibility.

If the air pollution is really a problem, shouldn't the locals address this problem for the sake of public health?

This is something I don't understand. Is it possible that the air pollution doesn't create health problem, but only creates cognitive problem?

There was article here not so long ago linking how pollution affects IQ so I am more and more convinced that in the times where air is polluted by smoke and microplastics there can be a benefit of installing filters, if it is something that costs 600 dollars per classroom to fit two Dyson air filters it makes sense to spend this kind of money even to ease breathing for kids with Asthma

I can't figure out what kind of common air filter would filter out natural gas?! Am I won't out would they have never worked for their intended purpose?

You are correct. The best you can do would be an activated carbon filter, which some better filters have. However, if I am reading/interpreting the graphs correctly, this is talking about over four miles from the leak. You'd be in the 2-5 ppm range (based on surveys) or less for NG (ethane and methane). so, maybe some reduction, but I doubt it would have a physiological effect.

That may be still in the range for mercaptan tracer gas olfaction, in which case carbon would decrease the smell, but that's about it.

Damn auto correct. "Am I wrong or"..

You should still be able to edit your comment. There's a two-hour window.

Thanks for posting this. The tl;dr is:

> I don’t think the correct summary of the above study is: “A large effect was found. But this was a small study, it’s preliminary data, so let’s gather more information.” Rather, I think a better summary is: “The data showed no effect. A particular statistical analysis of these data seemed to show a large effect, but that was a mistake. Perhaps it’s still worth studying the problem because of other things we know about air pollution, in which case this particular study is irrelevant to the discussion.”

> The point is that these data, analyzed appropriately, do not show any clear effect. So if it’s a good idea to keep on with this, it’s in spite of, not because of these results.

Better than the other article by far.

Anyone with expertise in this field care to comment? It seems too good to be true?

Another problem that is becoming more of an issue recently is that the "energy efficient sealing" of rooms is causing carbon dioxide to rise higher than expected. Installing air filters may be a proxy for mixing carbon dioxide better with outside air. <shrug>

In short, this study has no real controls, a lot of problems, and not a lot of evidence.

As a side note, it is not like the kids live in the classroom, they are exposed nonetheless - when outside the classroom - to "normal" air, let's say that in a week they are 30 hours or less in class and the remaining 138 hours they are not.

So these magical filtering allows for intellectual improvements when impacting roughly 30/168=17.8% less than 20% of inhaled air?

That's the whole point of the article. The author proposes a new title, "New study finds no evidence of educational benefits from installing air filters in classrooms."

Reply on news.ycombinator.com